CVE-2026-14534
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).
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.59%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
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.
- CVSS 3.1
- 8.8 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
- EPSS
- 0.59% probability · 47th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-184, CWE-502
- Affected
- trailofbits/fickling
- Source
- aa17e1a1-c329-4d6e-a1ed-8d0188aea082
References
- https://github.com/trailofbits/fickling/commit/e8408615b63adf034f891f653692ab9b51f0f5afPatch
- https://github.com/trailofbits/fickling/pull/272Issue Tracking, Patch
- https://github.com/trailofbits/fickling/releases/tag/v0.1.11Release Notes
- https://github.com/trailofbits/fickling/security/advisories/GHSA-m6fh-58r7-x697Exploit, Vendor Advisory
- https://github.com/trailofbits/fickling/security/advisories/GHSA-m6fh-58r7-x697Exploit, Vendor Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.