Headline
CVE-2023-28100: CVE-2023-28100: TIOCLINUX can send commands outside sandbox if running on a virtual console
Flatpak is a system for building, distributing, and running sandboxed desktop applications on Linux. Versions prior to 1.10.8, 1.12.8, 1.14.4, and 1.15.4 contain a vulnerability similar to CVE-2017-5226, but using the TIOCLINUX ioctl command instead of TIOCSTI. If a Flatpak app is run on a Linux virtual console such as /dev/tty1, it can copy text from the virtual console and paste it into the command buffer, from which the command might be run after the Flatpak app has exited. Ordinary graphical terminal emulators like xterm, gnome-terminal and Konsole are unaffected. This vulnerability is specific to the Linux virtual consoles /dev/tty1, /dev/tty2 and so on. A patch is available in versions 1.10.8, 1.12.8, 1.14.4, and 1.15.4. As a workaround, don’t run Flatpak on a Linux virtual console. Flatpak is primarily designed to be used in a Wayland or X11 graphical environment.
Impact
If a Flatpak app is run on a Linux virtual console such as /dev/tty1, it can copy text from the virtual console and paste it into the command buffer, from which the command might be run after the Flatpak app has exited. This is similar to CVE-2017-5226, but using the TIOCLINUX ioctl command instead of TIOCSTI.
Ordinary graphical terminal emulators like xterm, gnome-terminal and Konsole are unaffected. This vulnerability is specific to the Linux virtual consoles /dev/tty1, /dev/tty2 and so on, which are not commonly used to run Flatpak apps.
Patches
8e63de9
See the flatpak-1.14.x, flatpak-1.12.x, flatpak-1.10.x branches for backports of this change to older codebases.
Workarounds
Don’t run Flatpak on a Linux virtual console. Flatpak is primarily designed to be used in a Wayland or X11 graphical environment.
References
https://marc.info/?l=oss-security&m=167879021709955&w=2
Related news
Gentoo Linux Security Advisory 202312-12 - Several vulnerabilities have been found in Flatpack, the worst of which lead to privilege escalation and sandbox escape. Versions greater than or equal to 1.14.4 are affected.
The bubblewrap sandbox of WebKitGTK and WPE WebKit, prior to 2.28.3, failed to properly block access to CLONE_NEWUSER and the TIOCSTI ioctl. CLONE_NEWUSER could potentially be used to confuse xdg-desktop-portal, which allows access outside the sandbox. TIOCSTI can be used to directly execute commands outside the sandbox by writing to the controlling terminal's input buffer, similar to CVE-2017-5226.
When executing a program via the bubblewrap sandbox, the nonpriv session can escape to the parent session by using the TIOCSTI ioctl to push characters into the terminal's input buffer, allowing an attacker to escape the sandbox.