Description
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.
Problem types
CWE-693 Protection Mechanism Failure
Product status
Any version
0.1.12 (custom)
Credits
Christopher Aziz (Bombadil Systems LLC)
References
github.com/...ckling/security/advisories/GHSA-cffv-grgg-g429
github.com/...ckling/security/advisories/GHSA-cffv-grgg-g429 (GitHub Security Advisory GHSA-cffv-grgg-g429)
github.com/trailofbits/fickling/pull/278 (Fix PR #278 — Split shorten_code() formatting from dedup tracking, make MLAllowlist opt-in)
github.com/...ommit/41ce7cb01edd97072994039574a2301ebb3f463d (Fix commit 41ce7cb (squash merge of PR #278))
github.com/trailofbits/fickling/releases/tag/v0.1.12 (Fickling v0.1.12 release)