CVE-2024-42472Flatpak may allow access to files outside sandbox for certain apps

Official description

Flatpak is a Linux application sandboxing and distribution framework. Prior to versions 1.14.0 and 1.15.10, a malicious or compromised Flatpak app using persistent directories could access and write files outside of what it would otherwise have access to, which is an attack on integrity and confidentiality. When `persistent=subdir` is used in the application permissions (represented as `--persist=subdir` in the command-line interface), that means that an application which otherwise doesn't have access to the real user home directory will see an empty home directory with a writeable subdirectory `subdir`. Behind the scenes, this directory is actually a bind mount and the data is stored in the per-application directory as `~/.var/app/$APPID/subdir`. This allows existing apps that are not aware of the per-application directory to still work as intended without general home directory access. However, the application does have write access to the application directory `~/.var/app/$APPID` where this directory is stored. If the source directory for the `persistent`/`--persist` option is replaced by a symlink, then the next time the application is started, the bind mount will follow the symlink and mount whatever it points to into the sandbox. Partial protection against this vulnerability can be provided by patching Flatpak using the patches in commits ceec2ffc and 98f79773. However, this leaves a race condition that could be exploited by two instances of a malicious app running in parallel. Closing the race condition requires updating or patching the version of bubblewrap that is used by Flatpak to add the new `--bind-fd` option using the patch and then patching Flatpak to use it. If Flatpak has been configured at build-time with `-Dsystem_bubblewrap=bwrap` (1.15.x) or `--with-system-bubblewrap=bwrap` (1.14.x or older), or a similar option, then the version of bubblewrap that needs to be patched is a system copy that is distributed separately, typically `/usr/bin/bwrap`. This configuration is the one that is typically used in Linux distributions. If Flatpak has been configured at build-time with `-Dsystem_bubblewrap=` (1.15.x) or with `--without-system-bubblewrap` (1.14.x or older), then it is the bundled version of bubblewrap that is included with Flatpak that must be patched. This is typically installed as `/usr/libexec/flatpak-bwrap`. This configuration is the default when building from source code. For the 1.14.x stable branch, these changes are included in Flatpak 1.14.10. The bundled version of bubblewrap included in this release has been updated to 0.6.3. For the 1.15.x development branch, these changes are included in Flatpak 1.15.10. The bundled version of bubblewrap in this release is a Meson "wrap" subproject, which has been updated to 0.10.0. The 1.12.x and 1.10.x branches will not be updated for this vulnerability. Long-term support OS distributions should backport the individual changes into their versions of Flatpak and bubblewrap, or update to newer versions if their stability policy allows it. As a workaround, avoid using applications using the `persistent` (`--persist`) permission.

Affected packages & fixed versions

Affected products (as reported)

References

• https://github.com/flatpak/flatpak/security/advisories/GHSA-7hgv-f2j8-xw87 x_refsource_CONFIRM
• https://github.com/containers/bubblewrap/commit/68e75c3091c87583c28a439b45c45627a94d622c x_refsource_MISC
• https://github.com/containers/bubblewrap/commit/a253257cd298892da43e15201d83f9a02c9b58b5 x_refsource_MISC
• https://github.com/flatpak/flatpak/commit/2cdd1e1e5ae90d7c3a4b60ce2e36e4d609e44e72 x_refsource_MISC
• https://github.com/flatpak/flatpak/commit/3caeb16c31a3ed62d744e2aaf01d684f7991051a x_refsource_MISC
• https://github.com/flatpak/flatpak/commit/6bd603f6836e9b38b9b937d3b78f3fbf36e7ff75 x_refsource_MISC
• https://github.com/flatpak/flatpak/commit/7c63e53bb2af0aae9097fd2edfd6a9ba9d453e97 x_refsource_MISC
• https://github.com/flatpak/flatpak/commit/8a18137d7e80f0575e8defabf677d81e5cc3a788 x_refsource_MISC
• https://github.com/flatpak/flatpak/commit/db3a785241fda63bf53f0ec12bb519aa5210de19 x_refsource_MISC
• http://www.openwall.com/lists/oss-security/2024/08/14/6
• https://lists.debian.org/debian-lts-announce/2025/03/msg00025.html