Vulnerability · Published Jan 20, 2026 · Assigned by mitre
CVE-2025-56005
Critical 9.8
In plain English
A critical-severity unsafe deserialization in the ply package (Debian). Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 18.8% (higher than 97% of all known vulnerabilities). Ready-made attack tooling exists: public proof-of-concept code.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | ply | no fix listed | DEBIAN-CVE-2025-56005 |
| Debian:13 | ply | no fix listed | DEBIAN-CVE-2025-56005 |
| Debian:14 | ply | no fix listed | DEBIAN-CVE-2025-56005 |
| Ubuntu:22.04:LTS | ply | no fix listed | UBUNTU-CVE-2025-56005 |
| Ubuntu:24.04:LTS | ply | no fix listed | UBUNTU-CVE-2025-56005 |
| Ubuntu:25.10 | ply | no fix listed | UBUNTU-CVE-2025-56005 |
Affected products (as reported)
Weakness: CWE-502 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
References
- https://github.com/bohmiiidd/Undocumented-RCE-in-PLY
- https://github.com/tom025/ply_exploit_rejection
- https://github.com/bohmiiidd/Undocumument_RCE_PLY-yacc-CVE-2025-56005
- https://github.com/tom025/ply_exploit_rejection/issues/1
- http://www.openwall.com/lists/oss-security/2026/01/23/4
- http://www.openwall.com/lists/oss-security/2026/01/23/5
- http://www.openwall.com/lists/oss-security/2026/01/28/5
- http://www.openwall.com/lists/oss-security/2026/01/29/1
- http://www.openwall.com/lists/oss-security/2026/01/29/2
- http://www.openwall.com/lists/oss-security/2026/01/30/1
- https://access.redhat.com/security/cve/CVE-2025-56005 vdb-entry, x_refsource_REDHAT
- RHBZ#2431308 issue-tracking, x_refsource_REDHAT
- https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-56005.json x_sadp-csaf-vex