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8.8

Fickling may load unsafe modules during pickle deserialization

CVE-2026-14535 · published 4 months ago
Summary

The Python tool fickling (versions up to 0.1.11) has a coding mistake that stops one of its safety checks from running. As a result, code that’s saved in a pickle file can bring in unexpected Python modules and be executed, even though the tool says the file looks safe. Update to a newer release or stop using fickling to load untrusted pickle data until the problem is fixed.

What to do

The CVE record does not list a fixed version. Check the vendor's site or the advisory links below - a fix may already be released.

Affected software
VendorProductAffected versions
trailofbits fickling <= 0.1.11
Original advisory text
Fickling MLAllowlist analysis pass rendered inoperative by shared mutable state in AnalysisContext.shorten_code()
In Trail of Bits fickling versions up to and including 0.1.11, the UnsafeImportsML analysis pass unconditionally calls AnalysisContext.shorten_code(node) on every import node it inspects, regardless of whether the import is flagged as unsafe. This call registers the shortened code representation in the shared AnalysisContext.reported_shortened_code set. When the MLAllowlist analysis pass subsequently runs, it calls the same shorten_code() method, receives already_reported=True for every import, and executes a continue statement that skips its allowlist check entirely. This renders MLAllowlist dead code for all imports — it never evaluates whether an import is in the ML allowlist or not. The MLAllowlist pass was designed to catch imports of modules outside the known-safe ML ecosystem (torch, numpy, transformers, etc.) that slip past the UnsafeImports denylist. With MLAllowlist inoperative, any standard library module not in the UNSAFE_IMPORTS denylist can be invoked via pickle deserialization while fickling's check_safety() returns LIKELY_SAFE. The fickling.load() API chains check_safety() into pickle.loads() as an explicit security gate, meaning a LIKELY_SAFE verdict causes the payload to be deserialized and executed. The root cause is shared mutable state between independently-correct analysis passes — UnsafeImportsML works as designed in isolation, MLAllowlist works as designed in isolation, but the shared reported_shortened_code set causes UnsafeImportsML to poison MLAllowlist's deduplication logic.
References
Fix within
Internet-facing 14 days
Internal At next upgrade
  • Not known to be exploited
  • Needs hands-on effort to exploit
  • Gives an attacker full control
Severity
8.8 High
Exploitation
<1% chance of attack within 30 days
Type
CWE-693Protection Mechanism Failure
Timeline
Published4 Jul 2026
Updated4 Nov 2026
First seen4 Jul 2026
Sources
CVE-2026-14535 · NVD
CVE-2026-14535 · MITRE
CVE-2026-14535 · OSV
GHSA-cffv-grgg-g429 · GHSA
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