CVE-2026-96808

Public on 2026-09-23
Modified on 2026-09-24
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.
Severity
Important severity
Important
See what this means
CVSS v3 Base Score
7.8
See breakdown

Affected Packages

Platform Package Release Date Advisory Status
Amazon Linux 2 - Core flatpak Not Affected
Amazon Linux 2023 flatpak Pending Fix
Amazon Linux 2027 Preview flatpak Not Affected
Amazon Linux 2023 flatpak-builder Not Affected
Amazon Linux 2027 Preview flatpak-builder Not Affected

CVSS Scores

Score Type Score Vector
Amazon Linux CVSSv3 7.8 CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H