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.
Does this matter?
EPSS puts the probability of exploitation in the next 30 days at 17.5%, higher than 97% of all known CVEs. Patch or mitigate before the next change window.
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 3.1
- 9.8 CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- EPSS
- 17.51% probability · 97th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-502
- Affected
- dabeaz/ply
- Source
- cve@mitre.org
References
- 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
- https://access.redhat.com/security/cve/CVE-2025-56005
- https://bugzilla.redhat.com/show_bug.cgi?id=2431308
- https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-56005.json
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.