Two critical vulnerabilities in Flatpak (CVE-2026-34078, CVSS 10.0, and CVE-2026-34079, CVSS 7.5) allow malicious or compromised sandboxed applications to access or delete arbitrary host files, potentially leading to host code execution. CVE-2026-34078 affects flatpak versions up to and including 1.16.3, while CVE-2026-34079 affects versions prior to 1.16.4. The fixed version for both issues is Flatpak 1.16.4.
It was discovered that Flatpak did not properly validate paths in sandbox-expose options. A malicious or compromised Flatpak app could use app-controlled symlinks to access arbitrary host files and gain code execution in the host context. This issue was addressed in Ubuntu Ubuntu 20.04 LTS, Ubuntu 22.04 LTS and Ubuntu 24.04 LTS. (CVE-2026-34078) It was discovered that Flatpak did not properly validate paths when removing outdated ld.so cache files. A malicious or compromised Flatpak app could use this issue to delete arbitrary files on the host. (CVE-2026-34079)