An undocumented and unsafe feature in the PLY (Python Lex-Yacc) library 3.11 allows Remote Code Execution (RCE) via the `picklefile` parameter in the `yacc()` function. This parameter accepts a `.pkl` file that is deserialized with `pickle.load()` without validation. Because `pickle` allows execution of embedded code via `__reduce__()`, an attacker can achieve code execution by passing a malicious pickle file. The parameter is not mentioned in official documentation or the GitHub repository, yet it is active in the PyPI version. This introduces a stealthy backdoor and persistence risk.
History

Tue, 20 Jan 2026 20:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'poc', 'Technical Impact': 'total'}, 'version': '2.0.3'}


Tue, 20 Jan 2026 19:30:00 +0000

Type Values Removed Values Added
Weaknesses CWE-502
Metrics cvssV3_1

{'score': 9.8, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'}


Tue, 20 Jan 2026 18:30:00 +0000

Type Values Removed Values Added
Description An undocumented and unsafe feature in the PLY (Python Lex-Yacc) library 3.11 allows Remote Code Execution (RCE) via the `picklefile` parameter in the `yacc()` function. This parameter accepts a `.pkl` file that is deserialized with `pickle.load()` without validation. Because `pickle` allows execution of embedded code via `__reduce__()`, an attacker can achieve code execution by passing a malicious pickle file. The parameter is not mentioned in official documentation or the GitHub repository, yet it is active in the PyPI version. This introduces a stealthy backdoor and persistence risk.
References

cve-icon MITRE

Status: PUBLISHED

Assigner: mitre

Published:

Updated: 2026-01-20T18:49:29.501Z

Reserved: 2025-08-16T00:00:00.000Z

Link: CVE-2025-56005

cve-icon Vulnrichment

Updated: 2026-01-20T18:48:39.836Z

cve-icon NVD

Status : Received

Published: 2026-01-20T19:15:49.247

Modified: 2026-01-20T19:15:49.247

Link: CVE-2025-56005

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

No data.