Patool versions prior to 4.0.5 contain a path traversal flaw where the safe_extract() function uses character‑level prefix checking to verify that extracted files remain within a target directory. When a malicious archive includes crafted member paths, the containment check can be bypassed, allowing the attacker to write files anywhere on the filesystem. This capability can be used to inject malicious binaries, or modify configuration files, potentially leading to escalation of privileges or remote code execution.

The vulnerability affects the Patool archive handling library distributed by wummel. All releases older than 4.0.5 are vulnerable. The issue is triggered when running Patool under Python versions prior to 3.12, and is mitig.0.5 and later releases.

The CVSS base score is 5.3, indicating moderate severity. EPSS data is not available, and the vulnerability is not listed in the CISA KEV catalog. The attack requires local execution of Patool with the ability to provide a crafted archive, so the likely vector is a local or privileged user. If Patool is invoked as part of an automated service that processes untrusted archives, the risk of exploitation increases substantially. Once exploited, arbitrary file writes can confidentiality, facilitating further attacks.