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 18.8%, 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
- 18.81% probability · 97th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-502
- Affected
- dabeaz/ply
- Source
- cve@mitre.org
EPSS 18.8% since 30 October 2026; no change recorded yet. The dashed line is the ten per cent mark our analysts treat as “patch before the next change window”. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
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, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.