CVE-2026-14534: Fickling on Python 0.1.10 and earlier allows malicious code execution

Summary

Fickling versions up to 0.1.10 fail to block certain standard library modules, which can lead to malicious code being executed when deserializing untrusted data. To fix this, update to a version of fickling that includes these modules in its denylist. This is a security risk because it allows attackers to inject and run malicious code.

What to do

No fix is available yet. Check with your software vendor for updates.

Affected software

Vendor	Product	Affected versions
trailofbits	fickling	<= 0.1.10

Original title

Trail of Bits fickling versions up to and including 0.1.10 do not include the Python standard library modules _posixsubprocess, site, and atexit in the UNSAFE_IMPORTS denylist (fickle.py). Because ...

Original description

Trail of Bits fickling versions up to and including 0.1.10 do not include the Python standard library modules _posixsubprocess, site, and atexit in the UNSAFE_IMPORTS denylist (fickle.py). Because these modules are absent from the denylist, fickling's check_safety() function returns LIKELY_SAFE with zero findings for pickle payloads that invoke dangerous functions including _posixsubprocess.fork_exec (C-level process spawner capable of executing arbitrary binaries), site.execsitecustomize (executes arbitrary site customization code), and atexit._run_exitfuncs (triggers all registered exit handler callbacks). The fickling.load() API chains check_safety() into pickle.loads() as an explicit security gate; a LIKELY_SAFE verdict causes the payload to be deserialized and executed. This shares the same root cause as CVE-2026-22607 (cProfile), CVE-2025-67748 (pty), and CVE-2025-67747 (marshal/types). OvertlyBadEvals does not flag these modules because they are standard library imports. UnsafeImports does not flag them because they are not in the denylist. The UnusedVariables heuristic is defeated by the SETITEMS opcode pattern.

mitre CVSS3.1 8.8

Vulnerability type

CWE-184

CWE-502 Deserialization of Untrusted Data