CVE-2025-56005
CRITICALCVSS Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Lifecycle Timeline
4Description
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.
Analysis
PLY (Python Lex-Yacc) library 3.11 has an unsafe feature enabling remote code execution through pickle deserialization of cached parser tables, with EPSS 0.91%.
Technical Context
PLY 3.11 uses Python's pickle module to cache parser tables (CWE-502). Since pickle deserialization can execute arbitrary Python code, an attacker who can write to PLY's cache directory or supply crafted parser tables can achieve code execution.
Affected Products
['PLY (Python Lex-Yacc) 3.11']
Remediation
Update PLY if a patched version is available. Verify integrity of parser cache files. Run applications with minimal file system permissions.
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External POC / Exploit Code
Leaving vuln.today