Vulnerability in Flatpak

[ Description ]Official description

In Flatpak before 1.18.1, the revokefs writer, used by the flatpak-system-helper to receive repository data from unprivileged callers, validated file paths by rejecting literal .. components but did not prevent symlink traversal. A malicious local user in an active local session could obtain two revokefs sessions via the system helper, create a symlink in one session pointing into the other session's directory, and retain a file descriptor through that symlink. This allowed the attacker to modify files belonging to a different revokefs session after they had been validated and imported by the system helper. In particular, an attacker could use this to tamper with ostree commit objects in the system repository after they passed signature verification, enabling root-controlled file writes to attacker-chosen paths and local root privilege escalation.

[ Fixes ]Fixes and patches

No fix or interim patch is linked from our sources yet. Check the vendor references below and limit exposure of affected systems until a fix is available.

[ Advisories ]Government CERT advisories

• BSI CERT-Bund11 Oct 2026WID-SEC-2026-3861

  Red Hat Enterprise Linux (flatpak): Multiple vulnerabilities Translated from German

  CVE-2026-90616CVE-2026-96808CVE-2026-86320+2 more CVEs

[ References ]References

• github.com/flatpak/flatpak/security/advisories/GHSA-qrwq-7qwx-q9rp