12.07.19

From Moderate Advice to FUD and Misinformation: The Case of a VPN Vulnerability (CVE-2019-14899)

Posted in FUD, GNU/Linux, Security at 1:16 pm by Dr. Roy Schestowitz

Sometimes it morphes to “Linux” and a false description of what’s happening

Summary: What should have been a trivial bugfix in a variety of operating systems and bits of software — both proprietary and Free software — somehow became anti-Linux FUD, clickbait and worse

EARLIER in the week I saw a report about CVE-2019-14899. There was nothing exciting about it. I mentioned it briefly and then moved on. But the following day and especially two days later (after the announcement [1]) the press was absolutely flooding with reports, especially from insecurity companies and anti-Linux sites [2-22]. At times even deliberate lies were spread [23] (there are no attacks). See below a roughly chronological list/timeline. The initial report was calm and rational.

“The only shocking thing isn’t the bug but the level of media attention it has received.”When one carefully examines what’s at stake, the patching status (it’s not a zero-day hole), the severity and risk level etc. one begins to wonder what motivated all this attention. Much more severe issues are being discovered each week if not month.

We first mentioned this 2 or 3 days ago, without even filing it as a high-priority Daily Links pick. The only shocking thing isn’t the bug but the level of media attention it has received. This is not the first time such a thing happens. When similar issues affect Windows the media just describes these as “computer issues” or “PC”. █

Related/contextual items from the news:

1. VPN hijacking on Linux (and beyond) systems

   Hi all,
   
   I am reporting a vulnerability that exists on most Linux distros, and
   other  *nix operating systems which allows a network adjacent attacker
   to determine if another user is connected to a VPN, the virtual IP
   address they have been assigned by the VPN server, and whether or not
   there is an active connection to a given website. Additionally, we are
   able to determine the exact seq and ack numbers by counting encrypted
   packets and/or examining their size. This allows us to inject data into
   the TCP stream and hijack connections.
   
   Most of the Linux distributions we tested were vulnerable, especially
   Linux distributions that use a version of systemd pulled after November
   28th of last year which turned reverse path filtering off. However, we
   recently discovered that the attack also works against IPv6, so turning
   reverse path filtering on isn't a reasonable solution, but this was how
   we discovered that the attack worked on Linux.
   
   Adding a prerouting rule to drop packets destined for the client's
   virtual IP address is effective on some systems, but I have only tested
   this on my machines (Manjaro 5.3.12-1, Ubuntu 19.10 5.3.0-23). This
   rule was proposed by Jason Donenfeld, and an analagous rule on the
   output chain was proposed by Ruoyu "Fish" Wang of ASU. We have some
   concerns that inferences can still be made using slightly different
   methods, but this suggestion does prevent this particular attack.
   
   There are other potential solutions being considered by the kernel
   maintainers, but I can't speak to their current status. I will provide
   updates as I receive them.
   
   I have attached the original disclosure I provided to 
   distros@vs.openwall.org and security@kernel.org below, with at least
   one critical correction: I orignally listed CentOS as being vulnerable
   to the attack, but this was incorrect, at least regarding IPv4. We
   didn't know the attack worked against IPv6 at the time we tested
   CentOS, and I haven't been able to test it yet.
   
   
   William J. Tolley
   Beau Kujath
   Jedidiah R. Crandall
   
   Breakpointing Bad &
   University of New Mexico
   
   
   *************************************************
   
   
   **General Disclosure:
   
   We have discovered a vulnerability in Linux, FreeBSD, OpenBSD, MacOS,
   iOS, and Android which allows a malicious access point, or an adjacent
   user,  to determine if a connected user is using a VPN, make positive
   inferences about the websites they are visiting, and determine the
   correct sequence and acknowledgement numbers in use, allowing the bad
   actor to inject data into the TCP stream. This provides everything that
   is needed for an attacker to hijack active connections inside the VPN
   tunnel.
   
   This vulnerability works against OpenVPN, WireGuard, and IKEv2/IPSec,
   but has not been thoroughly tested against tor, but we believe it is
   not vulnerable since it operates in a SOCKS layer and includes
   authentication and encryption that happens in userspace. It should be
   noted, however, that the VPN technology used does not seem to matter
   and we are able to make all of our inferences even though the responses
   from the victim are encrypted, using the size of the packets and number
   of packets sent (in the case of challenge ACKs, for example) to
   determine what kind of packets are being sent through the encrypted VPN
   tunnel.
   
   We have already reported a related vulnerability to Android earlier
   this year related to the issue, which resulted in the assignment of
   CVE-2019-9461, however, the CVE strictly applies to the fact that the
   Android devices would respond to unsolicited packets sent to the user’s
   virtual IP address over the wireless interface, but this does not
   address the fundamental issue of the attack and did not result in a
   change of the reverse path settings of Android as of the most recent
   security update.
   
   This attack did not work against any Linux distribution we tested until
   the release of Ubuntu 19.10, and we noticed that the rp_filter settings
   were set to “loose” mode. We see that the default settings in
   sysctl.d/50-default.conf in the systemd repository were changed from
   “strict” to “loose” mode on November 28, 2018, so distributions using a
   version of systemd without modified configurations after this date are
   now vulnerable. Most Linux distributions we tested which use other init
   systems leave the value as 0, the default for the Linux kernel.
   
   We have described the procedure for reproducing the vulnerability with
   Linux and included a section illustrating the differences in
   architecture.
   
   
   
   There are 3 steps to this attack:
   
   1. Determining  the  VPN  client’s virtual IP address
   2. Using the virtual IP address to make inferences about active
   connections
   3. Using the encrypted replies to unsolicited packets to determine the
   sequence and acknowledgment numbers of the active connection to hijack
   the TCP session
   
   
   
   There are 4 components to the reproduction:
   
   1. The Victim Device (connected to AP, 192.168.12.x, 10.8.0.8)
   2. AP (controlled by attacker, 192.168.12.1)
   3. VPN Server (not controlled by attacker, 10.8.0.1)
   4. A Web Server (not controlled by the attacker, public IP in a real-
   world scenario)
   
   The victim device connects to the access point, which for most of our
   testing was a laptop running create_ap. The victim device then
   establishes a connection with their VPN provider.
   
   The access point can then determine the virtual IP of the victim by
   sending SYN-ACK packets to the victim device across the entire virtual
   IP space (the default for OpenVPN is 10.8.0.0/24). When a SYN-ACK is
   sent to the correct virtual IP on the victim device, the device
   responds with a RST; when the SYN-ACK is sent to the incorrect virtual
   IP, nothing is received by the attacker.
   
   To quickly demonstrate this difference, we use the nping commands on
   the AP device running create_ap. The source IP is the gateway of our
   AP, the destination IP is the virtual IP assigned to the tun interface
   by the VPN client, ap0 is the interface create_ap created on the
   attacker device, and the destination MAC is the victim’s wireless MAC
   address.
   
   For example:
   
   The correct address generates a RST from the victim:
   
   nping --tcp --flags SA --source-ip 192.168.12.1 --dest-ip 10.8.0.8 --
   rate 3 -c 3 -e ap0 --dest-mac 08:00:27:9c:53:12
   
   The incorrect address does not elicit a response from the victim:
   
   nping --tcp --flags SA --source-ip 192.168.12.1 --dest-ip 10.8.0.9 --
   rate 3 -c 3 -e ap0 --dest-mac 08:00:27:9c:53:12
   
   Similarly, to test if there is an active connection for any given
   website, such as 64.106.46.56, for example, we send SYN or SYN-ACKs
   from 64.106.46.56 on port 80 (or 443) to the virtual IP of the victim
   across the entire ephemeral port space of the victim. The correct four-
   tuple will elicit no more than 2 challenge ACKs per second from the
   victim, whereas the victim will respond to the incorrect four-tuple
   with a RST for each packet sent to it.
   
   To quickly test this, we suggest creating a netcat connection on the
   victim device, such as this:
   
   Netcat 64.106.46.56 80 -p 40404
   
   The correct four-tuple generates challenge ACKs
   
   nping --tcp --flags SA --source-ip 64.106.46.56 -g 80 --dest-ip
   10.8.0.8 -p 40404 --rate 10 -c 10 -e ap0 --dest-mac 08:00:27:9c:53:12
   
   The incorrect four-tuple generates a single RST for each packet sent:
   
   nping --tcp --flags SA --source-ip 64.106.46.56 -g 80 --dest-ip
   10.8.0.8 -p 40405 --rate 10 -c 10 -e ap0 --dest-mac 08:00:27:9c:53:12
   
   Finally, once the attacker determined that the user has an active TCP
   connection to an external server,  we will attempt to infer the exact
   next sequence number and in-window acknowledgment number needed to
   inject forged packets into the connection. To find the appropriate
   sequence and ACK numbers, we will trigger responses from the client in
   the encrypted connection found in part 2. The attacker will continually
   spoof reset packets into the inferred connection until it sniffs
   challenge ACKs. The attacker can reliably determine if the packets
   flowing from the client to the VPN server are challenge ACKs by looking
   at the size and timing of the encrypted responses in relation to the
   attacker's spoofed packets. The victim’s device will trigger a TCP
   challenge ACK on each reset it receives that has an in-window sequence
   number for an existing connection. For example, if the client is using
   OpenVPN to exchange encrypted packets with the VPN server, then the
   client will always respond with an SSL packet of length 79 when a
   challenge ACK is triggered.
   
   The attacker must spoof resets to different blocks across the entire
   sequence number space until one triggers an encrypted challenge ACK.
   The size of the spoof block plays a significant role in how long the
   sequence inference takes, but should be conservative as to not skip
   over the receive window of the client. In practice, when the attacker
   thinks it sniffs an encrypted challenge-ACK, it can verify this is true
   by spoofing X packets with the same sequence number. If there were X
   encrypted responses with size 79 triggered, then the attacker knows for
   certain it is triggering challenge ACKs (at most 2 packets of size 79
   per second).
   
   After the attacker has inferred the in-window sequence number for the
   client's connection, they can quickly determine the exact sequence
   number and in-window ACK needed to inject. First, they spoof empty
   push-ACKs with the in-window sequence while guessing in-window ACK
   numbers. Once the spoofed packets trigger another challenge-ACK, an in-
   window ACK number is found. Finally, the attacker continually spoofs
   empty TCP data packets with the in-window ACK and sequence numbers as
   it decrements the sequence number after each send. The victim will
   respond with another challenge ACK once the attacker spoofs the exact
   sequence number minus one. The attacker can now inject arbitrary
   payloads into the ongoing encrypted connection using the inferred ACK
   and next sequence number.
   
   This can be tested by observing the behavior from this sequence of
   commands, continuing with the same four-tuple:
   
   Using the four-tuple from the previous steps, we send RSTs in the
   sequence number range in blocks of 50,000 until we trigger a challenge
   ACK.
   
   nping --tcp --flags R --source-ip 64.106.46.56 -g 80 --dest-ip 10.8.0.8
   -p 40404 --rate 10 -c 10 -e ap0 --dest-mac 08:00:27:9c:53:12 --seq [SEQ
   RANGE]
   
   If the packet lands in-window, the victim will respond with at most 2
   challenge ACKs per second. These packets are still encrypted and
   originate from the virtual interface, unlike with Android, but we can
   still determine the contents of these packets by their size. The
   encrypted challenge ACK packets are larger than the encrypted RST
   packets. You can run tcpdump on the victim machine to accelerate the
   testing of his process by viewing the actual sequence and
   acknowledgement numbers.
   
   After we have found an in-window sequence number, we locate an in-
   window acknowledgement by spoofing empty PSH-ACKs with the in-window
   sequence number and guessing the acknowledgement number by dividing the
   acknowledgement number space into eight blocks. In most instances,
   seven of these blocks will trigger challenge ACKs, but one of them will
   not, which allows us to quickly determine which block falls within the
   acknowledgement window. We are interested in the block that  does not
   respond with a challenge ACK. This behavior can be observed by using an
   in-window sequence number and an acknowledgement number in the block
   containing the correct acknowledgement number.
   
   nping --tcp --flags PA --source-ip 64.106.46.56 -g 80 --dest-ip
   10.8.0.8 -p 40404 --rate 10 -c 10 -e ap0 --dest-mac 08:00:27:9c:53:12
   -seq 12345678 --ack [ACK RANGE]
   
   Finally, using the in-window sequence and acknowledgement numbers, we
   spoof empty PSH-ACKs using the same in-windows acknowledgement number
   and decrementing the sequence number until we trigger another challenge
   ACK. This sequence number is one fewer than the next expected sequence
   number. We can then arbitrarily inject data into the active TCP
   connection.
   
   Continuing with our toy example:
   
   nping --tcp --flags PA --source-ip 64.106.46.56 -g 80 --dest-ip
   10.8.0.8 -p 40404 --rate 10 -c 10 -e ap0 --dest-mac 08:00:27:9c:53:12
   -seq [EXACT] --ack [IN-WINDOW] --data-string “hello,world.”
   
   
   
   **Operating Systems Affected:
   
   Here is a list of the operating systems we have tested which are
   vulnerable to this attack:
   
   Ubuntu 19.10 (systemd)
   Fedora (systemd)
   Debian 10.2 (systemd)
   Arch 2019.05 (systemd)
   Manjaro 18.1.1 (systemd)
   
   Devuan (sysV init)
   MX Linux 19 (Mepis+antiX)
   Void Linux (runit)
   
   Slackware 14.2 (rc.d) 
   Deepin (rc.d)
   FreeBSD (rc.d) 
   OpenBSD (rc.d) 
   
   This list isn’t exhaustive, and we are continuing to test other
   distributions, but made usere to cover a variety of init systems to
   show this is not limited to systemd.
   
   
   
   **Operating System Variations:
   
   The behavior is slightly different on other operating systems. Here is
   a summary of the differences:
   
   Android: In the first phase of the attack, Android responds with
   unencrypted RSTs to unsolicited SYN-ACKs for the correct port and ICMP
   packets for the incorrect one. For the second phase, it will respond
   with RSTs on the correct four-tuple.
   
   MacOS/iOS: The first phase of the attack does not work as described
   here, but you can use an open port on the Apple machine to determine
   the virtual IP address. We use port 5223, which is used for iCloud,
   iMessage, FaceTime, Game Center, Photo Stream, and push notifications
   etc.
   
   We know the phone will communicate with one of the push notification
   servers on port 5223, and have observed that on MacOS, the port used on
   the victim device is not the same as the port used to connect to the
   VPN server, but is very close (in our testing it has always been within
   10).
   
   nping --tcp --flags SA --source-ip 17.57.144.[84-87] -g 5223 --dest-ip
   10.8.0.8 -p [X] --rate 3 -c 3 -e ap0 --dest-mac 08:00:27:9c:53:12
   
   For iOS devices, it does not follow this convention for choosing the
   client’s source port, but always choose a port between ~48000-50000
   (our testing on iOS 13.1 was between 48162-49555).
   
   FreeBSD: The first two phases work essentially the same as Linux,
   however, for the last phase, the ACK number is not needed at all, so
   that piece of phase three can be skipped.
   
   OpenBSD: OpenBSD responds to spoofed SYN packets to the correct virtual
   IP with unencrypted RST packets, and the incorrect virtual IP elicits
   unencrypted NTP packets or nothing at all for the first part of the
   attack. For the second part, the responses are encrypted, but we can
   still determine which packets are challenge ACKs from the packet size,
   as with Linux. Connections can be reset by sending a RST with the
   correct sequence number.
   
   
   
   **Possible Mitigations:
   
   1. Turning reverse path filtering on
   
   Potential problem: Asynchronous routing not reliable on mobile devices,
   etc. Also, it isn’t clear that this is actually a solution since it
   appears to work in other OSes with different networking stacks. Also,
   even with reverse path filtering on strict mode, the first two parts of
   the attack can be completed, allowing the AP to make inferences about
   active connections, and we believe it may be possible to carry out the
   entire attack, but haven’t accomplished this yet.
   
   2. Bogon filtering
   
   Potential problem: Local network addresses used for vpns and local
   networks, and some nations, including Iran, use the reserved private IP
   space as part of the public space.
   
   3. Encrypted packet size and timing
   
   Since the size and number of packets allows the attacker to bypass the
   encryption provided by the VPN service, perhaps some sort of padding
   could be added to the encrypted packets to make them the same size.
   Also, since the challenge ACK per process limit allows us to determine
   if the encrypted packets are challenge ACKs, allowing the host to
   respond with equivalent-sized packets after exhausting this limit could
   prevent the attacker from making this inference.
   
   
   We have prepared a paper for publication concerning this
   vulnerability and the related implications, but intend to keep it
   embargoed until we have found a satisfactory workaround. Then we will
   report the vulnerability to oss-security@lists.openwall.com. We are
   also reporting this vulnerability to the other services affected, which
   also includes: Systemd, Google, Apple, OpenVPN, and WireGuard, in
   addition to distros@vs.openwall.org for the operating systems affected.
   
   Thanks,
   
   William J. Tolley
   Beau Kujath
   Jedidiah R. Crandall
   
   Breakpointing Bad &
   University of New Mexico
   

2. New Vulnerability Lets Attackers Hijack VPN Connections on Most UNIX Systems

   Affecting most GNU/Linux distributions, as well as FreeBSD, OpenBSD, Android, iOS and macOS systems, the new security vulnerability could allow a local attacker to determine if another user is connected to a VPN (Virtual Private Network) server and whether or not there’s an active connection to a certain website.

   The vulnerability (CVE-2019-14899) is exploitable with adjacent network access, which requires the attacker to have access to either the broadcast or collision domain of the vulnerable operating system, and lets attackers to hijack connections by injecting data into the TCP (Transmission Control Protocol) stream.

   The vulnerability has been reported to work against various popular VPN solutions, including OpenVPN, IKEv2/IPSec, as well as WireGuard, and it doesn’t matter which VPN technology is being used, thus allowing attacker to determine the type of packets being sent through the encrypted VPN tunnel.

3. Tricky VPN-busting bug lurks in iOS, Android, Linux distros, macOS, FreeBSD, OpenBSD, say university eggheads

   A bug in the way Unix-flavored systems handle TCP connections could put VPN users at risk of having their encrypted traffic hijacked, it is claimed.

   The University of New Mexico team of William Tolley, Beau Kujath, and Jedidiah Crandall this week said they’ve discovered CVE-2019-14899, a security weakness they report to be present in “most” Linux distros, along with Android, iOS, macOS, FreeBSD, and OpenBSD. The upshot is, if exploited, encrypted VPN traffic can be potentially hijacked and disrupted by miscreants on the network.

   To pull off the attack, the US-based posse says, a hacker would need to be “network adjacent” to their target, or control an access point on the victim’s local network. Once the victim connected to their VPN, the spy would be able to, for one thing, tamper with the TCP stream to do things like inject packets into the stream.

4. New Linux Vulnerability Lets Attackers Hijack VPN Connections

   Security researchers found a new vulnerability allowing potential attackers to hijack VPN connections on affected *NIX devices and inject arbitrary data payloads into IPv4 and IPv6 TCP streams. They disclosed the security flaw tracked as CVE-2019-14899 to distros and the Linux kernel security team, as well as to others impacted such as Systemd, Google, Apple, OpenVPN, and WireGuard. The vulnerability is known to impact most Linux distributions and Unix-like operating systems including FreeBSD, OpenBSD, macOS, iOS, and Android. A currently incomplete list of vulnerable operating systems and the init systems they came with is available below, with more to be added once they are tested and found to be affected: Ubuntu 19.10 (systemd), Fedora (systemd), Debian 10.2 (systemd), Arch 2019.05 (systemd), Manjaro 18.1.1 (systemd), Devuan (sysV init), MX Linux 19 (Mepis+antiX), Void Linux (runit), Slackware 14.2 (rc.d), Deepin (rc.d), FreeBSD (rc.d), and OpenBSD (rc.d).

5. New Linux Vulnerability Lets Attackers Hijack VPN Connections

   Security researchers found a new vulnerability allowing potential attackers to hijack VPN connections on affected *NIX devices and inject arbitrary data payloads into IPv4 and IPv6 TCP streams.

   They disclosed the security flaw tracked as CVE-2019-14899 to distros and the Linux kernel security team, as well as to others impacted such as Systemd, Google, Apple, OpenVPN, and WireGuard.

6. New vulnerability lets attackers sniff or hijack VPN connections

   The vulnerability — tracked as CVE-2019-14899 — resides in the networking stacks of multiple Unix-based operating systems, and more specifically, in how the operating systems reply to unexpected network packet probes.

7. Hackers Can Hijack VPN Connections Using A New Linux Vulnerability

   Researchers have found a vulnerability on most Linux distros and *NIX devices which allow hackers to hijack the VPN connections and inject malicious data into the TCP stream.

   The security researchers found the vulnerability in most Linux distributions and operating systems such as Linux, FreeBSD, OpenBSD, macOS, iOS, and Android.

8. Linux security flaw could let VPN connections be hacked

   The Breakpointing Bad cybersecurity research team from the University of New Mexico discovered and reported on a security flaw which could allow malicious actors to hack Virtual Private Network (VPN) connections.

   William J. Tolley, Beau Kujath, and Jedidiah R. Crandall said the flaw impacts Linux, Android, macOS and other Unix-based operating systems and could allow attackers to sniff, hijack and tamper with VPN-tunnelled connections. The vulnerability was named CVE-2019-14899, with the researchers claiming it takes advantage of how operating systems handle unexpected network probes.

9. Linux Flaw Allows VPN Hijacking

   A number of Linux distributions, including Ubuntu, Fedora, and Debian, contain a newly discovered vulnerability that an attacker could use to determine whether an individual is using a VPN and then potentially hijack that encrypted connection.

   A research team from the University of New Mexico discovered the vulnerability and developed an attack to exploit it. The attack has some specific requirements and relies on some analysis of the traffic going to and from the target device running the VPN client. The attack is confirmed to work against WireGuard and OpenVPN, but the researchers said that the VPN a victim is using doesn’t really matter. The main prerequisite for the attack to work is for the attacker to be able to send unsolicited packets to the victim’s VPN client.

10. New Linux vulnerability lets attackers to hijack VPN connections

    Three researchers from the University of New Mexico and Breakpointing Bad have identified vulnerability in the way Unix and Linux-based operating systems like the macOS handle the TCIP connections. Researchers believe that vulnerability can specifically affect VPN users by hijacking encrypted traffic.

11. New Linux Bug Lets Attackers Hijack Encrypted VPN Connections

    A team of cybersecurity researchers has disclosed a new severe vulnerability affecting most Linux and Unix-like operating systems, including FreeBSD, OpenBSD, macOS, iOS, and Android, that could allow remote ‘network adjacent attackers’ to spy on and tamper with encrypted VPN connections.
    The vulnerability, tracked as CVE-2019-14899, resides in the networking stack of various operating systems and can be exploited against both IPv4 and IPv6 TCP streams.
    Since the vulnerability does not rely on the VPN technology used, the attack works against widely implemented virtual private network protocols like OpenVPN, WireGuard, IKEv2/IPSec, and more, the researchers confirmed.
    This vulnerability can be exploited by a network attacker — controlling an access point or connected to the victim’s network — just by sending unsolicited network packets to a targeted device and observing replies, even if they are encrypted.

12. VPN Bug Affects “Most” Linux Distros

    A team of security researchers from the University of New Mexico has disclosed a new vulnerability that could allow attackers to probe devices and determine various details about the VPN (Virtual Private Network) connection status of a user.

    The security vulnerability (CVE-2019-14899) appears to affect most GNU/Linux distributions, besides FreeBSD, OpenBSD, Android, iOS and macOS systems. William J. Tolley, one of the security researchers, explained in a post that the vulnerability could let attackers to determine if another user is connected to a VPN, the virtual IP address they have been assigned by the VPN server, and also sniff out whether or not there is an active connection to a given website.

13. OpenBSD devs patch authentication bypass bug

    One of the internet’s most popular free operating systems allowed attackers to bypass its authentication controls, effectively leaving the keys in the back door, according to an advisory released this week. The developers of the OpenBSD system have already patched the vulnerability.

    OpenBSD allowed people access to its smtpd, ldapd, and radiusd programs – which send mail, allow access to user directories, and allow remote access to the computer system. All an attacker needed to do was enter a specific word prefixed by a hyphen as a username.

    Qualys Research Labs found four bugs in BSD Authentication, which is the code that OpenBSD uses to authenticate users. Three of them were local privilege escalation bugs, while the other, CVE-2019-19521, bypassed the authentication system altogether. According to its security advisory, BSD Authentication supports four authentication styles: password, a one-time password mechanism called S/Key, and Yubico’s YubiKey hardware token.

14. New Linux vulnerability puts VPN connections at risk of hijacking

    Furthermore, the research team also identified the SEQ and ACK numbers from inspecting the encrypted packet size and number and managed to inject data into the TCP steam, which led to the hijacking of the connection. This means VPN technology was ineffective in preventing the attack since even encrypted packets could be assessed.

    After testing on Manjaro 18.1.1, CentOS, and Ubuntu 19, researchers discovered that the exploit was applicable to both IPv4 and IPv6. Other systems that are vulnerable to exploitation include Void Linux, Debian 10.2, Slackware 14.2, Arch 2019.5, MX Linux 19, Deepin, Fedora, Devuan, FreeBSD, and OpenBSD. They will be testing the effectiveness of the exploit against Tor as well.

15. Attackers using Linux Vulnerability to Hijack VPN Connections

16. Linux VPN connections can be hacked

    Insecurity experts at Breakpointing Bad have found aa new vulnerability allowing potential attackers to hijack VPN connections on affected *NIX devices and inject arbitrary data payloads into IPv4 and IPv6 TCP streams.

    The security flaw tracked as CVE-2019-14899 to distros and the Linux kernel security team, as well as to others impacted such as Systemd, Google, Apple, OpenVPN, and WireGuard. The vulnerability is known to impact most Linux distributions and Unix-like operating systems including FreeBSD, OpenBSD, macOS, iOS, and Android.

    A currently incomplete list of vulnerable operating systems and the init systems they came with is available below, with more to be added once they are tested and found to be affected: Ubuntu 19.10 (systemd), Fedora (systemd), Debian 10.2 (systemd), Arch 2019.05 (systemd), Manjaro 18.1.1 (systemd), Devuan (sysV init), MX Linux 19 (Mepis+antiX), Void Linux (runit), Slackware 14.2 (rc.d), Deepin (rc.d), FreeBSD (rc.d), and OpenBSD (rc.d).

17. VPN connections could be hacked due to Linux security flaw

    A new vulnerability that could allow potential attackers to hijack VPN connections on affected NIX devices and inject arbitrary data payloads into IPv4 and Ipv6 TCP streams has been discovered by security researchers.

    The researchers disclosed the security flaw they detected, tracked as CVE-2019-14899, to Linux distro makers, the Linux kernel security team and to others that are impacted including systemd, Google, Apple, OpenVPN and WireGuard.

18. Unix-like Systems Vulnerable to VPN Inferring and Hijacking Attacks

    Three researchers from Breakpointing Bad and the University of New Mexico have discovered a vulnerability that exists in Linux and Unix-like operating systems like Android and macOS. Given the tracking code “CVE-2019-14899”, the flaw resides in the routing table code and the TCP code that is present in these systems. The vulnerability allows an attacker to perform traffic analysis via clever use of encrypted DNS queries in conjunction with error messages, leading to the sniffing of open TCP connection information. The attack was discovered quite a while back, but the researchers disclosed it publicly now, and after they allowed the vendors some time to plug the holes.

19. Researchers say VPN bug affects Linux, Unix systems

20. Linux Bug Opens Most VPNs to Hijacking

    In a coffee-shop scenario, attackers can hijack “secure” VPN sessions of those working remotely, injecting data into their TCP streams.

    A vulnerability in most Linux distros has been uncovered that allows a network-adjacent attacker to hijack VPN connections and inject rogue data into the secure tunnels that victims are using to communicate with remote servers.

    According to researchers at University of New Mexico and Breakpointing Bad, the bug (CVE-2019-14899), “allows…an attacker to determine if…a user is connected to a VPN, the virtual IP address they have been assigned by the VPN server, and whether or not there is an active connection to a given website.”

21. New vulnerability lets attackers sniff or hijack VPN connections

22. Researchers find a new Linux vulnerability that allows attackers to sniff or hijack VPN connections

    On Wednesday, security researchers from the University of New Mexico disclosed a vulnerability impacting most Linux distributions and Unix-like operating systems including FreeBSD, OpenBSD, macOS, iOS, and Android. This Linux vulnerability can be exploited by an attacker to determine if a user is connected to a VPN and to hijack VPN connections.

    The researchers shared that this security flaw tracked as CVE-2019-14899, “allows a network adjacent attacker to determine if another user is connected to a VPN, the virtual IP address they have been assigned by the VPN server, and whether or not there is an active connection to a given website.” Additionally, attackers can determine the exact sequence and acknowledgment numbers by counting encrypted packets or by examining their size. With this information in hand, they can inject arbitrary data payloads into IPv4 and IPv6 TCP streams.

23. Hackers Exploit New Linux Vulnerability To Hijack VPN Connections

    The attack has been reported to work against several popular VPN solutions, including OpenVPN, IKEv2/IPSec, and WireGuard.

    However, the researchers are still testing their viability against Tor, as it works in a SOCKS layer and implements authentication and encryption that takes place in userspace.

    “It should be noted, however, that the VPN technology used does not seem to matter and we are able to make all of our inferences even though the responses from the victim are encrypted, using the size of the packets and number of packets sent (in the case of challenge ACKs, for example) to determine what kind of packets are being sent through the encrypted VPN tunnel,” clarifies the research team.

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