{"id":"CVE-2026-96637","title":"Pillow: Decompression bomb check bypass in SpiderImagePlugin.seek() leads to unbounded allocation DoS","summary":"Pillow is a Python imaging library. Prior to 13.0.0, SpiderImageFile.seek() in src/PIL/SpiderImagePlugin.py reparses a later SPIDER stack frame and replaces self._size without rerunning Image._decompression_bomb_check(). A tiny file can …","severity":"high","cvss":7.1,"cvssVector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N","cvssSource":"cna","cwe":["CWE-400","CWE-409"],"vendor":"python-pillow","product":"Pillow","affected":["Pillow < 13.0.0"],"published":"2026-10-21","updated":"2026-10-21","sourceUpdated":"2026-10-21T21:01:20.249Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-96637","references":[{"url":"https://github.com/python-pillow/Pillow/security/advisories/GHSA-g842-9rc4-69pw","label":"https://github.com/python-pillow/Pillow/security/advisories/GHSA-g842-9rc4-69pw"},{"url":"https://github.com/python-pillow/Pillow/pull/10076","label":"https://github.com/python-pillow/Pillow/pull/10076"},{"url":"https://github.com/python-pillow/Pillow/commit/7cb0e02389d8aac2a60896a490f572db0b07b841","label":"https://github.com/python-pillow/Pillow/commit/7cb0e02389d8aac2a60896a490f572db0b07b841"},{"url":"https://github.com/python-pillow/Pillow/releases/tag/13.0.0","label":"https://github.com/python-pillow/Pillow/releases/tag/13.0.0"}],"tags":["cve.org"],"ingestedAt":"2026-10-21T22:18:33.801Z","slug":"CVE-2026-96637","body":"## Overview\n\nPillow is a Python imaging library. Prior to 13.0.0, SpiderImageFile.seek() in src/PIL/SpiderImagePlugin.py reparses a later SPIDER stack frame and replaces self._size without rerunning Image._decompression_bomb_check(). A tiny file can use a safe first frame to pass Image.open() and then declare very large dimensions in a later mode F frame. Loading that frame allocates approximately four bytes per attacker-declared pixel and can consume multiple gigabytes of memory. This issue is fixed in version 13.0.0.\n\n## Affected\n\n- `Pillow < 13.0.0`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"twilight","depthScore":39,"depthScoreParts":{"impact":39.1,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}