{"api_version":"1","generated_at":"2026-10-31T02:21:37+00:00","cve":"CVE-2026-16760","urls":{"html":"https://cve.report/CVE-2026-16760","api":"https://cve.report/api/cve/CVE-2026-16760.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-16760","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-16760"},"summary":{"title":"Fickling check_safety() bypass: likely_safe_imports grants module-origin trust to unvalidated standard library callables","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.","state":"PUBLISHED","assigner":"BombadilSystems","published_at":"2026-10-30 22:16:54","updated_at":"2026-10-30 22:16:54"},"problem_types":["CWE-502","CWE-693","CWE-693 CWE-693 Protection Mechanism Failure","CWE-502 CWE-502 Deserialization of Untrusted Data"],"metrics":[{"version":"3.1","source":"aa17e1a1-c329-4d6e-a1ed-8d0188aea082","type":"Secondary","score":"8.8","severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","data":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","baseScore":8.8,"baseSeverity":"HIGH","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"REQUIRED","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"}},{"version":"3.1","source":"CNA","type":"CVSS","score":"8.8","severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","data":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"HIGH","baseScore":8.8,"baseSeverity":"HIGH","confidentialityImpact":"HIGH","integrityImpact":"HIGH","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"REQUIRED","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","version":"3.1"}}],"references":[{"url":"https://github.com/trailofbits/fickling","name":"https://github.com/trailofbits/fickling","refsource":"aa17e1a1-c329-4d6e-a1ed-8d0188aea082","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://github.com/trailofbits/fickling/commit/d011709","name":"https://github.com/trailofbits/fickling/commit/d011709","refsource":"aa17e1a1-c329-4d6e-a1ed-8d0188aea082","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://bombadil.systems/advisories.html","name":"https://bombadil.systems/advisories.html","refsource":"aa17e1a1-c329-4d6e-a1ed-8d0188aea082","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://pypi.org/project/fickling/0.1.12/","name":"https://pypi.org/project/fickling/0.1.12/","refsource":"aa17e1a1-c329-4d6e-a1ed-8d0188aea082","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-16760","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-16760","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"trailofbits","product":"fickling","version":"affected 0.1.12 custom","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[{"source":"CNA","value":"Christopher Aziz (Bombadil Systems LLC)","lang":"en"}],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"collectionURL":"https://pypi.org/project/fickling/","defaultStatus":"unaffected","packageName":"fickling","product":"fickling","vendor":"trailofbits","versions":[{"lessThanOrEqual":"0.1.12","status":"affected","version":"0","versionType":"custom"}]}],"credits":[{"lang":"en","type":"finder","value":"Christopher Aziz (Bombadil Systems LLC)"}],"descriptions":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"<p>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.</p>"}],"value":"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."}],"impacts":[{"descriptions":[{"lang":"en","value":"An attacker can craft a malicious pickle that invokes a dangerous callable imported from a standard library module not present in UNSAFE_IMPORTS. The name is added to likely_safe_imports by _process_import(), causing OvertlyBadEvals to skip the call, so check_safety() returns LIKELY_SAFE and fickling.load() proceeds to deserialize the payload. This yields arbitrary code execution via dataclasses._create_fn or mailcap.findmatch on Python versions through 3.12, and arbitrary file write with attacker-controlled content via readline.write_history_file on POSIX platforms across supported Python versions. Because the flaw is in the module-origin trust model rather than in any specific module list, adding the demonstrated modules to UNSAFE_IMPORTS does not address the root cause; additional dangerous callables remain reachable through other non-blocked standard library modules."}]}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"HIGH","baseScore":8.8,"baseSeverity":"HIGH","confidentialityImpact":"HIGH","integrityImpact":"HIGH","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"REQUIRED","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","version":"3.1"},"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}]}],"problemTypes":[{"descriptions":[{"cweId":"CWE-693","description":"CWE-693 Protection Mechanism Failure","lang":"en","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-502","description":"CWE-502 Deserialization of Untrusted Data","lang":"en","type":"CWE"}]}],"providerMetadata":{"dateUpdated":"2026-10-30T21:16:31.353Z","orgId":"aa17e1a1-c329-4d6e-a1ed-8d0188aea082","shortName":"BombadilSystems"},"references":[{"name":"Bombadil Systems advisory listing","url":"https://bombadil.systems/advisories.html"},{"name":"fickling 0.1.12 on PyPI","url":"https://pypi.org/project/fickling/0.1.12/"},{"name":"fickling source repository","url":"https://github.com/trailofbits/fickling"},{"name":"Vendor remediation merge commit d011709 (adds readline, dataclasses, and mailcap to UNSAFE_IMPORTS on master; the module-origin trust root cause remains)","url":"https://github.com/trailofbits/fickling/commit/d011709"}],"source":{"discovery":"UNKNOWN"},"title":"Fickling check_safety() bypass: likely_safe_imports grants module-origin trust to unvalidated standard library callables","x_generator":{"engine":"Vulnogram 1.0.5"}}},"cveMetadata":{"assignerOrgId":"aa17e1a1-c329-4d6e-a1ed-8d0188aea082","assignerShortName":"BombadilSystems","cveId":"CVE-2026-16760","datePublished":"2026-10-30T21:16:31.353Z","dateReserved":"2026-07-23T14:00:36.878Z","dateUpdated":"2026-10-30T21:16:31.353Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-10-30 22:16:54","lastModifiedDate":"2026-10-30 22:16:54","problem_types":["CWE-502","CWE-693","CWE-693 CWE-693 Protection Mechanism Failure","CWE-502 CWE-502 Deserialization of Untrusted Data"],"metrics":{"cvssMetricV31":[{"source":"aa17e1a1-c329-4d6e-a1ed-8d0188aea082","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","baseScore":8.8,"baseSeverity":"HIGH","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"REQUIRED","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"},"exploitabilityScore":2.8,"impactScore":5.9}]},"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"16760","Ordinal":"1","Title":"Fickling check_safety() bypass: likely_safe_imports grants modul","CVE":"CVE-2026-16760","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"16760","Ordinal":"1","NoteData":"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.","Type":"Description","Title":"Fickling check_safety() bypass: likely_safe_imports grants modul"}]}}}