Executive brief
Red Hat libuser is a system library used to manage user and group accounts on Linux systems. A race condition in how it writes to the password database (/etc/passwd) allows local users with valid system access to cause service outages or gain elevated privileges through file corruption. This vulnerability has already been exploited by attackers in real-world scenarios.
Technical details
The vulnerability is a race condition in Red Hat libuser's handling of the /etc/passwd file during user/group account modifications. An authenticated local attacker can exploit a time-of-check-time-of-use (TOCTOU) window in the file writing mechanism to corrupt critical password database entries. The attack requires local system access and can be triggered by performing rapid or concurrent account operations. Successful exploitation allows an attacker to deny service by corrupting password entries or escalate privileges by injecting malicious account data. The vulnerability has already been exploited in active attacks, indicating practical weaponization.
Affected products
- Red Hat Libuser <UNKNOWN>
Timeline
- 2026-08-26: disclosed
- exploited: Reported exploited in the wild