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.
EPSS 0.85% · 75.2th percentile
Risk Scores
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| dabeaz | ply | 3.11, 3.11 |
| n/a | n/a | n/a, n/a |
Timeline
- Jan 20, 2026 CVE Published
- Jan 20, 2026 PoC Published
- Jan 20, 2026 PoC Published
- Jan 21, 2026 EPSS Score
- Jan 23, 2026 PoC Published
- Jan 23, 2026 PoC Published
- Jan 23, 2026 PoC Published
- Jan 23, 2026 PoC Published
- Jan 23, 2026 PoC Published
- Jan 23, 2026 PoC Published
- Jan 24, 2026 EPSS Score
- Jan 26, 2026 EPSS Score
References
- https://github.com/bohmiiidd/Undocumented-RCE-in-PLY url
- https://github.com/tom025/ply_exploit_rejection url
- https://github.com/bohmiiidd/Undocumument_RCE_PLY-yacc-CVE-2025-56005 url
- https://github.com/tom025/ply_exploit_rejection/issues/1 url
- http://www.openwall.com/lists/oss-security/2026/01/23/4 url
- http://www.openwall.com/lists/oss-security/2026/01/23/5 url
- http://www.openwall.com/lists/oss-security/2026/01/28/5 url
- http://www.openwall.com/lists/oss-security/2026/01/29/1 url
- http://www.openwall.com/lists/oss-security/2026/01/29/2 url
- http://www.openwall.com/lists/oss-security/2026/01/30/1 url
- https://nvd.nist.gov/vuln/detail/CVE-2025-56005 advisory