Fence Agents Remediation Operator: Deserialization of Untrusted Data
CVE-2025-56005 is a high-severity deserialization of untrusted data vulnerability in Fence Agents Remediation Operator from Red Hat, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. There is no confirmed exploitation so far. EPSS estimates a 18.8% chance of exploitation within 30 days, which is in the top 2.67% of all scored CVEs.
EPSS places it among the vulnerabilities most likely to be exploited soon.
What to do
- Check which version of Fence Agents Remediation Operator you run against the affected versions below, and install the vendor's latest release.
Affected products and versions
Version data comes from the organisation that assigned the CVE; 3 further products are omitted here. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by CNA.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 9.8 | Critical | CISA (ADP) |
| CVSS 3.1 | 7.8 | High | CNA |
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.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Deserialization of Untrusted Data
The product deserializes untrusted data without sufficiently ensuring that the resulting data will be valid.
How developers prevent this class of flaw
- If available, use the signing/sealing features of the programming language to assure that deserialized data has not been tainted. For example, a hash-based message authentication code (HMAC) could be used to ensure that data has not been modified.
- When deserializing data, populate a new object rather than just deserializing. The result is that the data flows through safe input validation and that the functions are safe.
- Explicitly define a final object() to prevent deserialization.
More Deserialization of Untrusted Data vulnerabilities (CWE-502)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: poc, automatable: yes, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- github.com/tom025/ply_exploit_rejectionExploit, Mitigation, Third Party Advisory
Technical write-ups (may include proof of concept)
- github.com/bohmiiidd/Undocumented-RCE-in-PLYExploit, Third Party Advisory
- github.com/bohmiiidd/Undocumument_RCE_PLY-yacc-CVE-2025-56005Exploit, Third Party Advisory
- openwall.com/lists/oss-security/2026/01/23/4Exploit, Mailing List
- openwall.com/lists/oss-security/2026/01/28/5Exploit, Mailing List
- openwall.com/lists/oss-security/2026/01/29/1Exploit, Mailing List
Other references
- github.com/tom025/ply_exploit_rejection/issues/1
- openwall.com/lists/oss-security/2026/01/23/5Mailing List
- openwall.com/lists/oss-security/2026/01/29/2Mailing List
- openwall.com/lists/oss-security/2026/01/30/1
- access.redhat.com/security/cve/CVE-2025-56005
- bugzilla.redhat.com/show_bug.cgi?id=2431308
- security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-56005.json
Other vulnerabilities in Fence Agents Remediation Operator
- 7.5 High severity
- 8.2 High severity
- 7.5 High severity
Recent Deserialization of Untrusted Data vulnerabilities
- 8.1 High severity
- 9.8 Critical severity
- 9.8 Critical severity
- 7.8 High severity
- 7.8 High severity
- 8.8 High severity
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