CVEstrailofbitsCVE-2026-14534Published Jul 4, 13:25 · Updated Jul 6, 14:59 UTC
8.8
HighCVSS 3.1 · from BombadilSystems
CVE-2026-14534

Fickling check_safety() bypass via unlisted standard library modules (_posixsubprocess, site, atexit)

fickling · CWE-184 · CWE-184
Affectedfickling
FixUpdate to 0.1.11 or newer
PublishedJul 4, 13:25 · BombadilSystems
ScoredJul 4 · 8.8 · BombadilSystems
Exploit code publicNone known · checked 21:18 UTC
ExploitedNone known · CISA KEV checked 22:07 UTC

What we know

No known exploitation. CISA KEV, checked 22:07 UTC.
No public exploit code known. Exploit-DB, Metasploit, Nuclei, checked 21:18 UTC.
An attacker only needs network access to the target. No login needed. CVSS: network, no privileges.
Someone has to open, click or run something first. CVSS: user interaction required.
A successful attack can read and change data and take the service down. CVSS: high impact on confidentiality, integrity and availability.
A successful attack gives full control of the affected system. CISA: technical impact total.

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.

From BombadilSystems

Affected and fixed versions

ProductAffectedFixed inficklingup to 0.1.10–ficklingNot affected0.1.11

Exploit code

Exploit-DBnone knownMetasploitnone knownNucleinone known

References

GitHub Security Advisory GHSA-m6fh-58r7-x697 · github.comFix PR #272 · github.comFix commit e840861 · github.comFickling v0.1.11 release · github.com

Other CVEs in fickling

All 10 →
8.8Fickling check_safety() bypass: dotted __qualname__ in STACK_GLOBAL resolves a class-method attribute path that evades call analysis · CVE-2026-118938Oct 308.8Fickling check_safety() bypass: likely_safe_imports grants module-origin trust to unvalidated standard library callables · CVE-2026-16760Oct 308.8Fickling MLAllowlist analysis pass rendered inoperative by shared mutable state in AnalysisContext.shorten_code() · CVE-2026-14535Jul 4