Deserialization in Dabeaz Ply
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.
Vulnerability class: Insecure Deserialization
Published · last modified .
CVSS v3 metric
CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.191 (97.2th percentile), scored .
Moderate probability of exploitation in the next 30 days — watch for active exploitation reports. 97th percentile — 97.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.171 · newest: 0.191 · change: +0.019
Affected products
- Dabeaz Ply — versions 3.11
Weakness classification (CWE)
Public proof-of-concept exploits
References
- github.com/bohmiiidd/Undocumented-RCE-in-PLY (Exploit, Third Party Advisory)
- github.com/tom025/ply_exploit_rejection (Exploit, Third Party Advisory, Mitigation)
- github.com/bohmiiidd/Undocumument_RCE_PLY-yacc-CVE-2025-56005 (Exploit, Third Party Advisory)
- github.com/tom025/ply_exploit_rejection/issues/1
- af854a3a-2127-422b-91ae-364da2661108 (Exploit, Mailing List)
- af854a3a-2127-422b-91ae-364da2661108 (Mailing List)
- af854a3a-2127-422b-91ae-364da2661108 (Exploit, Mailing List)
- af854a3a-2127-422b-91ae-364da2661108 (Exploit, Mailing List)
- af854a3a-2127-422b-91ae-364da2661108 (Mailing List)
- af854a3a-2127-422b-91ae-364da2661108
Frequently asked questions
- What is CVE-2025-56005?
- CVE-2025-56005 is a critical-severity vulnerability in Dabeaz Ply, classified under Deserialization of Untrusted Data. CVSS score: 9.8/10. Published 2026-01-20.
- How severe is CVE-2025-56005?
- Critical severity. CVSS v3 base score is 9.8 out of 10.
- Is CVE-2025-56005 known to be exploited?
- 4 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.