CVE-2025-56005: ply · Deserialization of Untrusted Data
Affects plySource CVE Database V5
Not known to be exploited · 18% EPSS · CVSS 9.8 Critical.
Data as of 26 Oct 2026, 17:16 UTC
- EPSS
- 18.8% chance of exploitation in 30 days – higher than 97% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 20 Jan 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Affected software
| Product | Affected | Fixed in |
|---|---|---|
PyPIplypkg:pypi/plyOther threats | Affected
| Fixed in– |
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
Red Hat has not indicated an official patch or fix currently available for this vulnerability. Mitigation involves ensuring that applications do not use the undocumented 'picklefile' parameter or do not load pickle files from untrusted sources. Since exploitation requires the attacker to influence the pickle file, preventing untrusted file injection or modification is critical. Monitor vendor advisories for updates or patches.
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.
References
- github.com/bohmiiidd/Undocumented-RCE-in-PLY (opens in a new tab)
- github.com/tom025/ply_exploit_rejection (opens in a new tab)
- github.com/bohmiiidd/Undocumument_RCE_PLY-yacc-CVE-2025-56005 (opens in a new tab)
- github.com/tom025/ply_exploit_rejection/issues/1 (opens in a new tab)
- openwall.com/lists/oss-security/2026/01/23/4 (opens in a new tab)
- openwall.com/lists/oss-security/2026/01/23/5 (opens in a new tab)
- openwall.com/lists/oss-security/2026/01/28/5 (opens in a new tab)
- openwall.com/lists/oss-security/2026/01/29/1 (opens in a new tab)
- openwall.com/lists/oss-security/2026/01/29/2 (opens in a new tab)
- openwall.com/lists/oss-security/2026/01/30/1 (opens in a new tab)
- access.redhat.com/security/cve/CVE-2025-56005 (opens in a new tab)
- bugzilla.redhat.com/show_bug.cgi?id=2431308 (opens in a new tab)
- security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-56005.json (opens in a new tab)