THREATPORT/VULNERABILITY/CVE-2025-56005
CRITICAL SEVERITY

CVE-2025-56005

Ply vulnerability

CVSS
9.8
EPSS
16.9%
EPSS pct
97th
Exploited
No known
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 vendor
Dabeaz
Affected product
Ply
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness type (CWE)
  • CWE-502 — Deserialization of Untrusted Data
Published
2026-01-20

Risk analysis

Based on its CVSS vector, this vulnerability is exploitable over the network, low attack complexity, requiring no privileges, no user interaction. Successful exploitation leads to high impact to confidentiality, high impact to integrity, high impact to availability.

Its EPSS score of 16.9% reflects a moderate probability of exploitation activity in the wild over the next 30 days, placing it above 97% of all scored CVEs.

Check your external exposure to CVE-2025-56005

  • Confirm whether Dabeaz Ply is running on any internet-facing host or subdomain.
  • Match discovered service fingerprints against the version affected by CVE-2025-56005.
  • Prioritise remediation if the asset is public, business-critical, or near authentication/payment flows.

How ThreatPort helps with CVE-2025-56005

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