The Linux sandboxing framework Flatpak released security update 1.18.1 on 11 August 2026. It fixes ten CVEs – ranging from a complete sandbox escape with read/write access to the entire host filesystem to escalation to root privileges. Operators and users should update immediately.
The most serious flaws
- Sandbox escape via symlink: a malicious symlink in an app data directory could grant full read/write access to the host filesystem (GHSA-8688-9×26-hhxj).
- Root privilege escalation: path traversal in
revokefsallowed a local user to gain root. - Others: a possible buffer overflow on 32-bit systems, and an anti-downgrade policy bypass letting unprivileged users roll back system apps.
The sandbox escape is especially critical because Flatpak exists precisely to isolate untrusted applications from the system. Once that isolation is broken, the protection is gone. Alongside the stable 1.18.1, a 1.19.0 pre-release bundles the same fixes together with additional features.
What to do now
The update should be applied promptly across all distributions – especially where OCI images or untrusted applications are in use. Flatpak apps are updated with flatpak update; the framework itself comes via your distribution’s package manager. Restarting running Flatpak apps afterwards ensures the patched runtime takes effect.
Sources: linuxcompatible.org, Flatpak on GitHub.
