{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-16760", "assignerOrgId": "aa17e1a1-c329-4d6e-a1ed-8d0188aea082", "state": "PUBLISHED", "assignerShortName": "BombadilSystems", "dateReserved": "2026-07-23T14:00:36.878Z", "datePublished": "2026-10-30T21:16:31.353Z", "dateUpdated": "2026-10-30T21:16:31.353Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "aa17e1a1-c329-4d6e-a1ed-8d0188aea082", "shortName": "BombadilSystems", "dateUpdated": "2026-10-30T21:16:31.353Z"}, "title": "Fickling check_safety() bypass: likely_safe_imports grants module-origin trust to unvalidated standard library callables", "problemTypes": [{"descriptions": [{"lang": "en", "cweId": "CWE-693", "description": "CWE-693 Protection Mechanism Failure", "type": "CWE"}]}, {"descriptions": [{"lang": "en", "cweId": "CWE-502", "description": "CWE-502 Deserialization of Untrusted Data", "type": "CWE"}]}], "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."}]}], "affected": [{"vendor": "trailofbits", "product": "fickling", "collectionURL": "https://pypi.org/project/fickling/", "packageName": "fickling", "versions": [{"status": "affected", "version": "0", "lessThanOrEqual": "0.1.12", "versionType": "custom"}], "defaultStatus": "unaffected"}], "descriptions": [{"lang": "en", "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.", "supportingMedia": [{"type": "text/html", "base64": false, "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>"}]}], "references": [{"url": "https://bombadil.systems/advisories.html", "name": "Bombadil Systems advisory listing"}, {"url": "https://pypi.org/project/fickling/0.1.12/", "name": "fickling 0.1.12 on PyPI"}, {"url": "https://github.com/trailofbits/fickling", "name": "fickling source repository"}, {"url": "https://github.com/trailofbits/fickling/commit/d011709", "name": "Vendor remediation merge commit d011709 (adds readline, dataclasses, and mailcap to UNSAFE_IMPORTS on master; the module-origin trust root cause remains)"}], "metrics": [{"format": "CVSS", "scenarios": [{"lang": "en", "value": "GENERAL"}], "cvssV3_1": {"version": "3.1", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "REQUIRED", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH", "baseSeverity": "HIGH", "baseScore": 8.8, "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H"}}], "credits": [{"lang": "en", "value": "Christopher Aziz (Bombadil Systems LLC)", "type": "finder"}], "source": {"discovery": "UNKNOWN"}, "x_generator": {"engine": "Vulnogram 1.0.5"}}}}

{}

{"affected": [{"affectedData": [{"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"}]}], "source": "aa17e1a1-c329-4d6e-a1ed-8d0188aea082"}], "cveTags": [], "descriptions": [{"lang": "en", "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."}], "id": "CVE-2026-16760", "lastModified": "2026-10-30T22:16:54.193", "metrics": {"cvssMetricV31": [{"cvssData": {"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"}, "exploitabilityScore": 2.8, "impactScore": 5.9, "source": "aa17e1a1-c329-4d6e-a1ed-8d0188aea082", "type": "Secondary"}]}, "published": "2026-10-30T22:16:54.193", "references": [{"source": "aa17e1a1-c329-4d6e-a1ed-8d0188aea082", "url": "https://bombadil.systems/advisories.html"}, {"source": "aa17e1a1-c329-4d6e-a1ed-8d0188aea082", "url": "https://github.com/trailofbits/fickling"}, {"source": "aa17e1a1-c329-4d6e-a1ed-8d0188aea082", "url": "https://github.com/trailofbits/fickling/commit/d011709"}, {"source": "aa17e1a1-c329-4d6e-a1ed-8d0188aea082", "url": "https://pypi.org/project/fickling/0.1.12/"}], "sourceIdentifier": "aa17e1a1-c329-4d6e-a1ed-8d0188aea082", "vulnStatus": "Received", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-502"}, {"lang": "en", "value": "CWE-693"}], "source": "aa17e1a1-c329-4d6e-a1ed-8d0188aea082", "type": "Secondary"}]}

{}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "generic", "value": "[0,0.1.12]"}}], "enrichment": {"confidence": 95.0, "confidence_source": "inferred", "scores": [{"score": 95.0, "source": "inferred"}, {"score": 100.0, "source": "matching"}]}, "original": {"product": "fickling", "source": "cna", "vendor": "trailofbits"}, "product": "fickling", "vendor": "trailofbits"}], "created": "2026-10-30T22:30:13.722749+00:00", "updated": "2026-10-30T22:30:14.369078+00:00", "vendors": ["trailofbits", "trailofbits$PRODUCT$fickling"]}