Vulnerability Description
flatpak-builder is a tool to build flatpaks from source. From 1.4.5 to before 1.4.8, the license-files manifest key takes an array of paths to user defined licence files relative to the source directory of the module. The paths from that array are resolved using g_file_resolve_relative_path() and validated to stay inside the source directory using two checks - g_file_get_relative_path() which does not resolve symlinks and g_file_query_file_type() with G_FILE_QUERY_INFO_NOFOLLOW_SYMLINKS which only applies to the final path component. The copy operation runs on host. This can be exploited by using a crafted manifest and/or source to read arbitrary files from the host and capture them into the build output. This vulnerability is fixed in 1.4.8.
CVSS Score
MEDIUM
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Flatpak | Flatpak-Builder | >= 1.4.5, < 1.4.8 |
Related Weaknesses (CWE)
References
- https://github.com/flatpak/flatpak-builder/security/advisories/GHSA-6gm9-3g7m-39ExploitVendor Advisory
FAQ
What is CVE-2026-39977?
CVE-2026-39977 is a vulnerability with a CVSS score of 6.3 (MEDIUM). flatpak-builder is a tool to build flatpaks from source. From 1.4.5 to before 1.4.8, the license-files manifest key takes an array of paths to user defined licence files relative to the source directo...
How severe is CVE-2026-39977?
CVE-2026-39977 has been rated MEDIUM with a CVSS base score of 6.3/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-39977?
Check the references section above for vendor advisories and patch information. Affected products include: Flatpak Flatpak-Builder.