Deserialization of Untrusted Data Affecting rhcos package, versions *


Severity

Recommended
0.0
high
0
10

Based on Red Hat Enterprise Linux security rating.

Threat Intelligence

EPSS
0.95% (77th percentile)

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  • Snyk IDSNYK-RHEL9-RHCOS-15471522
  • published12 Mar 2026
  • disclosed20 Jan 2026

Introduced: 20 Jan 2026

CVE-2025-56005  (opens in a new tab)
CWE-502  (opens in a new tab)

How to fix?

There is no fixed version for RHEL:9 rhcos.

NVD Description

Note: Versions mentioned in the description apply only to the upstream rhcos package and not the rhcos package as distributed by RHEL. See How to fix? for RHEL:9 relevant fixed versions and status.

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 Base Scores

version 3.1