Vulnerability Description
Flatpak is a system for building, distributing, and running sandboxed desktop applications on Linux. In Flatpack since version 0.9.4 and before version 1.10.2 has a vulnerability in the "file forwarding" feature which can be used by an attacker to gain access to files that would not ordinarily be allowed by the app's permissions. By putting the special tokens `@@` and/or `@@u` in the Exec field of a Flatpak app's .desktop file, a malicious app publisher can trick flatpak into behaving as though the user had chosen to open a target file with their Flatpak app, which automatically makes that file available to the Flatpak app. This is fixed in version 1.10.2. A minimal solution is the first commit "`Disallow @@ and @@U usage in desktop files`". The follow-up commits "`dir: Reserve the whole @@ prefix`" and "`dir: Refuse to export .desktop files with suspicious uses of @@ tokens`" are recommended, but not strictly required. As a workaround, avoid installing Flatpak apps from untrusted sources, or check the contents of the exported `.desktop` files in `exports/share/applications/*.desktop` (typically `~/.local/share/flatpak/exports/share/applications/*.desktop` and `/var/lib/flatpak/exports/share/applications/*.desktop`) to make sure that literal filenames do not follow `@@` or `@@u`.
CVSS Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Flatpak | Flatpak | >= 0.9.4, < 1.10.2 |
| Debian | Debian Linux | 10.0 |
| Fedoraproject | Fedora | 33 |
Related Weaknesses (CWE)
References
- https://github.com/flatpak/flatpak/commit/8279c5818425b6812523e3805bbe242fb6a5d9PatchThird Party Advisory
- https://github.com/flatpak/flatpak/commit/a7401e638bf0c03102039e216ab1081922f140PatchThird Party Advisory
- https://github.com/flatpak/flatpak/commit/eb7946bb6248923d8c90fe9b84425fef97ae58PatchThird Party Advisory
- https://github.com/flatpak/flatpak/pull/4156PatchThird Party Advisory
- https://github.com/flatpak/flatpak/releases/tag/1.10.2Release NotesThird Party Advisory
- https://github.com/flatpak/flatpak/security/advisories/GHSA-xgh4-387p-hqppThird Party Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedorapro
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedorapro
- https://security.gentoo.org/glsa/202312-12
- https://www.debian.org/security/2021/dsa-4868Third Party Advisory
- https://github.com/flatpak/flatpak/commit/8279c5818425b6812523e3805bbe242fb6a5d9PatchThird Party Advisory
- https://github.com/flatpak/flatpak/commit/a7401e638bf0c03102039e216ab1081922f140PatchThird Party Advisory
- https://github.com/flatpak/flatpak/commit/eb7946bb6248923d8c90fe9b84425fef97ae58PatchThird Party Advisory
- https://github.com/flatpak/flatpak/pull/4156PatchThird Party Advisory
- https://github.com/flatpak/flatpak/releases/tag/1.10.2Release NotesThird Party Advisory
FAQ
What is CVE-2021-21381?
CVE-2021-21381 is a vulnerability with a CVSS score of 7.1 (HIGH). Flatpak is a system for building, distributing, and running sandboxed desktop applications on Linux. In Flatpack since version 0.9.4 and before version 1.10.2 has a vulnerability in the "file forwardi...
How severe is CVE-2021-21381?
CVE-2021-21381 has been rated HIGH with a CVSS base score of 7.1/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2021-21381?
Check the references section above for vendor advisories and patch information. Affected products include: Flatpak Flatpak, Debian Debian Linux, Fedoraproject Fedora.