Time-of-check Time-of-use (TOCTOU) Affecting libacl package, versions <0:2.4.0-1.amzn2023.0.1


Severity

Recommended
high

Based on Amazon Linux security rating.

Threat Intelligence

Social Trends
EPSS
0.09% (1st percentile)

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  • Snyk IDSNYK-AMZN2023-LIBACL-18065308
  • published21 Jul 2026
  • disclosed29 Jun 2026

Introduced: 29 Jun 2026

NewCVE-2026-54370  (opens in a new tab)
CWE-367  (opens in a new tab)

How to fix?

Upgrade Amazon-Linux:2023 libacl to version 0:2.4.0-1.amzn2023.0.1 or higher.
This issue was patched in ALAS2023-2026-1986.

NVD Description

Note: Versions mentioned in the description apply only to the upstream libacl package and not the libacl package as distributed by Amazon-Linux. See How to fix? for Amazon-Linux:2023 relevant fixed versions and status.

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.

CVSS Base Scores

version 3.1