CVE-2025-56005

Vulnerability 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. NOTE: A third-party states that this vulnerability should be rejected because the proof of concept does not demonstrate arbitrary code execution and fails to complete successfully.

CVSS Score

Affected Products

Related Weaknesses (CWE)

References

• https://github.com/bohmiiidd/Undocumented-RCE-in-PLYExploitThird Party Advisory
• https://github.com/bohmiiidd/Undocumument_RCE_PLY-yacc-CVE-2025-56005ExploitThird Party Advisory
• https://github.com/tom025/ply_exploit_rejectionExploitMitigationThird Party Advisory
• https://github.com/tom025/ply_exploit_rejection/issues/1
• http://www.openwall.com/lists/oss-security/2026/01/23/4ExploitMailing List
• http://www.openwall.com/lists/oss-security/2026/01/23/5Mailing List
• http://www.openwall.com/lists/oss-security/2026/01/28/5ExploitMailing List
• http://www.openwall.com/lists/oss-security/2026/01/29/1ExploitMailing List
• http://www.openwall.com/lists/oss-security/2026/01/29/2Mailing List
• http://www.openwall.com/lists/oss-security/2026/01/30/1