acl before 2.4.0 Local Priv Esc via TOCTOU Symlink Race
CVE-2026-54370 Published on June 29, 2026
acl < 2.4.0 TOCTOU Symlink Traversal via getfacl/setfacl/chacl
acl before version 2.4.0 contains a time-of-check to time-of-use (TOCTOU) race condition vulnerability that allows local attackers to escalate privileges by replacing a pathname component with a symbolic link between an lstat() check and subsequent symlink-following operations such as stat(), chown(), chmod(), acl_get_file(), and acl_set_file(). Attackers who control a pathname component can redirect file access control list operations to arbitrary files when getfacl, setfacl, or chacl is invoked by a privileged process over an attacker-controlled path, resulting in local privilege escalation.
Vulnerability Analysis
CVE-2026-54370 is exploitable with local system access, and requires small amount of user privileges. This vulnerability is consided to have a high level of attack complexity. The potential impact of an exploit of this vulnerability is considered to have a high impact on confidentiality and integrity, and no impact on availability.
Weakness Type
What is a TOCTTOU Vulnerability?
The software checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check. This can cause the software to perform invalid actions when the resource is in an unexpected state. This weakness can be security-relevant when an attacker can influence the state of the resource between check and use. This can happen with shared resources such as files, memory, or even variables in multithreaded programs.
CVE-2026-54370 has been classified to as a TOCTTOU vulnerability or weakness.
Affected Versions
acl project acl:- Before 2.4.0 is affected.