{"id":"CVE-2026-16760","aliases":[],"cve":{"records":[{"id":"CVE-2026-16760","source":"BombadilSystems","state":"PUBLISHED","reasons":[],"replacements":[],"disputed":false,"unsupportedWhenAssigned":false,"reserved":"2026-07-23T14:00:36.878Z","published":"2026-10-30T21:16:31.353Z","modified":"2026-10-30T21:16:31.353Z"}],"publishers":[{"name":"BombadilSystems","role":"CNA","organizationId":"aa17e1a1-c329-4d6e-a1ed-8d0188aea082","modified":"2026-10-30T21:16:31.353Z"}],"references":[{"url":"https://bombadil.systems/advisories.html","tags":[],"source":"BombadilSystems"},{"url":"https://pypi.org/project/fickling/0.1.12/","tags":[],"source":"BombadilSystems"},{"url":"https://github.com/trailofbits/fickling","tags":[],"source":"BombadilSystems"},{"url":"https://github.com/trailofbits/fickling/commit/d011709","tags":[],"source":"BombadilSystems"}],"weaknesses":[{"id":"CWE-693","description":"CWE-693 Protection Mechanism Failure","source":"BombadilSystems"},{"id":"CWE-502","description":"CWE-502 Deserialization of Untrusted Data","source":"BombadilSystems"}],"applicability":[],"prioritization":[]},"title":"Fickling check_safety() bypass: likely_safe_imports grants module-origin trust to unvalidated standard library callables","titleSource":"BombadilSystems","descriptionSource":"BombadilSystems","description":"In Trail of Bits fickling through 0.1.12, the _process_import() method in fickle.py adds an imported name to the likely_safe_imports set whenever the source module is present in sys.stdlib_module_names and the name is absent from the UNSAFE_IMPORTS denylist, without inspecting what the name resolves to or how it behaves. The OvertlyBadEvals analysis pass in analysis.py then unconditionally skips any call whose function name appears in likely_safe_imports, including calls that would otherwise be flagged as overtly dangerous. As a result, any callable reachable through a non-blocked standard library module inherits module-level trust regardless of its own behavior, and check_safety() returns LIKELY_SAFE with zero findings for pickle payloads that reach code execution or file write through such callables. Demonstrated primitives: dataclasses._create_fn, which passes an attacker-controlled function body to exec() and yields arbitrary code execution on Python 3.7 through 3.12 (the internal _create_fn function was removed in Python 3.13); mailcap.findmatch, which internally calls os.system() on a test command taken from an attacker-controlled caps dictionary, yielding arbitrary code execution on Python versions through 3.12 (the mailcap module was removed in Python 3.13); and readline.add_history() followed by readline.write_history_file(), which writes attacker-controlled content to an arbitrary filesystem path (POSIX platforms, where the readline module is available). fickling.load() chains check_safety() into pickle.loads() as an explicit security gate, so a LIKELY_SAFE verdict causes the payload to be deserialized and executed with the privileges of the victim process. The root cause is the inference of callable safety from module origin; it is independent of, and separately fixable from, the dotted __qualname__ resolution weakness tracked as CVE-2026-118938, which this advisory does not address. As of 2026-10-30 the three demonstrated modules were added to UNSAFE_IMPORTS on the vendor master branch (commit d011709) pending release; released versions through 0.1.12 remain affected, and the module-origin trust root cause persists, as demonstrated by the related CVE-2026-118938 remaining exploitable on that same build.","score":8.8,"severity":"high","published":"2026-10-30T21:16:31.353Z","modified":"2026-10-30T21:16:31.353Z","withdrawn":false,"knownExploited":false,"affected":[],"products":[{"vendor":"trailofbits","name":"fickling","platforms":[],"versions":[{"version":"0","status":"affected","lessThanOrEqual":"0.1.12","versionType":"custom"}],"defaultStatus":"unaffected","cpes":[],"source":"BombadilSystems","url":"https://www.cve.org/CVERecord?id=CVE-2026-16760"}],"remediation":[],"references":["https://bombadil.systems/advisories.html","https://pypi.org/project/fickling/0.1.12/","https://github.com/trailofbits/fickling","https://github.com/trailofbits/fickling/commit/d011709"],"sources":[{"name":"CVE","id":"CVE-2026-16760","modified":"2026-10-30T21:16:31.353Z","url":"https://www.cve.org/CVERecord?id=CVE-2026-16760"}],"assessments":[{"source":"BombadilSystems","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","score":8.8}],"sourceAffected":[],"observedAt":"2026-10-30T21:32:00.245Z","kev":{"status":"not-listed","checkedAt":"2026-10-31T14:00:31.626Z"},"coverage":[{"source":"NVD","status":"no-result","checkedAt":"2026-10-30T21:35:34.873Z","attemptedAt":"2026-10-30T21:35:34.873Z"},{"source":"GHSA","status":"no-result","checkedAt":"2026-10-30T21:35:34.843Z","attemptedAt":"2026-10-30T21:35:34.843Z"},{"source":"EUVD","status":"no-result","checkedAt":"2026-10-30T21:35:34.578Z","attemptedAt":"2026-10-30T21:35:34.578Z"},{"source":"EPSS","status":"no-result","checkedAt":"2026-10-30T21:35:34.612Z","attemptedAt":"2026-10-30T21:35:34.612Z"}],"evidence":[],"aiSummary":{"text":"Fickling through 0.1.12 has a vulnerability where the check_safety() function can be bypassed, allowing unvalidated standard library callables to be executed. This is due to the likely_safe_imports set granting module-origin trust to callables without inspecting their behavior. The impact of this vulnerability is that an attacker can execute arbitrary code or write to arbitrary filesystem paths.","model":"@cf/meta/llama-3.3-70b-instruct-fp8-fast","generatedAt":"2026-10-31T04:56:10.727Z","sources":[{"name":"CVE","url":"https://www.cve.org/CVERecord?id=CVE-2026-16760"}]}}