Path Traversal in Flatpak
CVE-2022-21682
Flatpak is a Linux application sandboxing and distribution framework. A path traversal vulnerability affects versions of Flatpak prior to 1.12.3 and 1.10.6. flatpak-builder applies `finish-args` last in the build. At this point the build directory will have the full access that is specified in the manifest, so running `flatpak build` against it will gain those permissions. Normally this will not be done, so this is not problem. However, if `--mirror-screenshots-url` is specified, then flatpak-builder will launch `flatpak build --nofilesystem=host appstream-utils mirror-screenshots` after finalization, which can lead to issues even with the `--nofilesystem=host` protection. In normal use, the only issue is that these empty directories can be created wherever the user has write permissions. However, a malicious application could replace the `appstream-util` binary and potentially do something more hostile. This has been resolved in Flatpak 1.12.3 and 1.10.6 by changing the behaviour of `--nofilesystem=home` and `--nofilesystem=host`.
Vulnerability class: Path Traversal (Directory Traversal)
EPSS: 0.017 (74.3th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 7.7 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:N.
Affected products
- Flatpak — versions >= 1.11.0, < 1.12.3, < 1.10.6
- Flatpak Flatpak-builder
- Debian Debian_linux — versions 9.0, 10.0, 11.0
- Fedoraproject Fedora — versions 35
- Redhat Enterprise_linux — versions 8.0
Weakness classification (CWE)
Public proof-of-concept exploits
References
- security-advisories@github.com (Patch, Third Party Advisory)
- security-advisories@github.com (Patch, Third Party Advisory)
- security-advisories@github.com (Patch, Third Party Advisory)
- security-advisories@github.com (vendor-advisory)
- security-advisories@github.com (vendor-advisory, Third Party Advisory)
- security-advisories@github.com (vendor-advisory)
- security-advisories@github.com (vendor-advisory)
Frequently asked questions
- What is CVE-2022-21682?
- CVE-2022-21682 is a high-severity vulnerability in Flatpak, classified under Path Traversal. CVSS score: 7.7/10. Published 2022-01-13.
- How severe is CVE-2022-21682?
- High severity. CVSS v3 base score is 7.7 out of 10.
- Is CVE-2022-21682 known to be exploited?
- 3 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.