Bug 2539569 (CVE-2026-96808) - CVE-2026-96808 flatpak: Flatpak: Local privilege escalation via symlink traversal in revokefs writer
Summary: CVE-2026-96808 flatpak: Flatpak: Local privilege escalation via symlink trave...
Keywords:
Status: NEW
Alias: CVE-2026-96808
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
high
high
Target Milestone: ---
Assignee: Product Security
QA Contact:
URL:
Whiteboard:
Depends On: 2539622
Blocks:
TreeView+ depends on / blocked
 
Reported: 2026-09-23 17:21 UTC by OSIDB Bzimport
Modified: 2026-09-23 18:25 UTC (History)
2 users (show)

Fixed In Version:
Clone Of:
Environment:
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Description OSIDB Bzimport 2026-09-23 17:21:34 UTC
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.


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