CVE-2025-67748: Trail of Bits Fickling code injection via pty.spawn bypass

CVE-2025-67748 · Severity: high · CVSS 7.8 · Published 2025-12-16

Fickling is a security tool used to analyze and detect malicious Python pickle files. A vulnerability was found where specially crafted malicious files could bypass Fickling's safety checks, leading the tool to incorrectly label them as safe. If a user then opens such a file based on this false assurance, an attacker could execute arbitrary code on the user's system.

Technologies: fickling (PyPI). Vendors: PyPI.

Quick answers

Is CVE-2025-67748 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2025-67748 being exploited in the wild.
How severe is CVE-2025-67748?
High severity, with a CVSS score of 7.8, published 16 December 2025.
Which products and versions are affected?
fickling (PyPI) < 0.1.6, ECOSYSTEM:introduced=0,fixed=0.1.6.
Is there a fix for CVE-2025-67748?
Yes. fickling (PyPI): upgrade to 0.1.6 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2025-67748 attacked?
It is attacked with local access, in a software library.
Am I affected by CVE-2025-67748?
Check whether you run fickling (PyPI) or Trailofbits Fickling at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • fickling (PyPI): upgrade to 0.1.6 or later
    pip install "fickling>=0.1.6"

Technical details

Fickling is vulnerable to a detection bypass that allows arbitrary code execution via unsafe deserialization. The issue stems from two root causes: the 'pty' module was missing from the blocklist of unsafe imports, and the 'unused variable' heuristic could be subverted. An attacker can bypass the heuristic by using the 'BUILD' opcode to 'use' a variable that would otherwise be left on the stack after a malicious operation (like REDUCE or INST). This causes Fickling to incorrectly categorize the file as 'LIKELY_SAFE'. The vulnerability is addressed in version 0.1.6 by updating the blocklist and improving detection logic.

Affected products

  • trailofbits fickling < 0.1.6

Identifiers

  • CVE-2025-67748
  • GHSA-r7v6-mfhq-g3m2
  • PYSEC-2025-113

Timeline

  • 2025-12-15: disclosed
  • 2025-12-15: advisory
  • 2025-12-15: patched: Fixed in version 0.1.6

References

This page as Markdown. Free to reuse under CC BY 4.0 with a link back.