CVE-2025-56005

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.

• CWE-502

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

Published

Jan 20, 2026

Last Modified

Jun 17, 2026

Status

Modified