CVE-2026-88924

A flaw was found in the admin backend of gvfs. The privileged gvfsd-admin daemon changes the ownership of newly created private D-Bus sockets by calling the link-following chown() function on a pathname inside a user-controlled directory. A local attacker can exploit this via a Time-of-Check Time-of-Use (TOCTOU) race condition and exchange the socket pathname with a symbolic link pointing to an arbitrary root-owned file (such as /etc/pam.d/su). The daemon subsequently follows the symlink and changes the ownership of the targeted root-owned file to the attacker's user ID. This allows an authenticated local attacker to modify critical system files, leading to a full local privilege escalation to root.

To exploit this issue, an attacker needs local access to the system and the ability to start the gvfsd-admin daemon. Furthermore, the attacker must successfully win a timing race condition, increasing the attack complexity. However, successful exploitation can allow the attacker to change the ownership of arbitrary system files, resulting in a full local privilege escalation to root. For these reasons, this vulnerability has been rated with an important severity.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

To mitigate this issue, adjust Polkit rules to require password authentication to start gvfsd-admin or remove execute permissions of the gvfsd-admin binary to prevent execution.