CVE-2026-39977

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.

The following products are affected by CVE-2026-39977 vulnerability.

Here, you will find a curated list of external links that provide in-depth information to CVE-2026-39977.

URL	Resource
https://github.com/flatpak/flatpak-builder/security/advisories/GHSA-6gm9-3g7m-3965