flatpak-builder: flatpak-builder is a tool to build flatpaks from source
CVE-2026-39977 is fixed in 2 products on 1 platform, first by flatpak-builder 1.4.8-1, released April 9, 2026. It is not reported as exploited. Patch Radar priority: Routine.
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.
Where it's fixed
| Product | Fixed in | Fix | Released |
|---|---|---|---|
| Linux | |||
| flatpak-builder · Debian 14 | 1.4.8-1 | DEBIAN-CVE-2026-39977 | Apr 9, 2026 |
| flatpak-builder · Ubuntu 26.04.1 LTS (resolute) | 1.4.8-1 | flatpak-builder 1.4.8-1 | Apr 9, 2026 |
| flatpak-builder-tests · Ubuntu 26.04.1 LTS (resolute) | 1.4.8-1 | flatpak-builder-tests 1.4.8-1 | Apr 9, 2026 |
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