CVE-2021-21381
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.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (1.55%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
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 3.1
- 8.2 HIGHCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N
- EPSS
- 1.55% probability · 74th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-74
- Affected
- flatpak/flatpak · debian/debian linux · fedoraproject/fedora
- Source
- security-advisories@github.com
References
- https://github.com/flatpak/flatpak/commit/8279c5818425b6812523e3805bbe242fb6a5d961Patch, Third Party Advisory
- https://github.com/flatpak/flatpak/commit/a7401e638bf0c03102039e216ab1081922f140aePatch, Third Party Advisory
- https://github.com/flatpak/flatpak/commit/eb7946bb6248923d8c90fe9b84425fef97ae580dPatch, Third Party Advisory
- https://github.com/flatpak/flatpak/pull/4156Patch, Third Party Advisory
- https://github.com/flatpak/flatpak/releases/tag/1.10.2Release Notes, Third Party Advisory
- https://github.com/flatpak/flatpak/security/advisories/GHSA-xgh4-387p-hqppThird Party Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/2MXXLXC2DPJ45HSMTI5MZYHMYEGQN6AA/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/WXNVFOIB6ZP4DGOVKAM25T6OIEP3YLGV/
- https://security.gentoo.org/glsa/202312-12
- https://www.debian.org/security/2021/dsa-4868Third Party Advisory
- https://github.com/flatpak/flatpak/commit/8279c5818425b6812523e3805bbe242fb6a5d961Patch, Third Party Advisory
- https://github.com/flatpak/flatpak/commit/a7401e638bf0c03102039e216ab1081922f140aePatch, Third Party Advisory
- https://github.com/flatpak/flatpak/commit/eb7946bb6248923d8c90fe9b84425fef97ae580dPatch, Third Party Advisory
- https://github.com/flatpak/flatpak/pull/4156Patch, Third Party Advisory
- https://github.com/flatpak/flatpak/releases/tag/1.10.2Release Notes, Third Party Advisory
- https://github.com/flatpak/flatpak/security/advisories/GHSA-xgh4-387p-hqppThird Party Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/2MXXLXC2DPJ45HSMTI5MZYHMYEGQN6AA/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/WXNVFOIB6ZP4DGOVKAM25T6OIEP3YLGV/
- https://security.gentoo.org/glsa/202312-12
- https://www.debian.org/security/2021/dsa-4868Third Party Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.