{"id":"CVE-2026-96640","title":"Pillow PDF append accepts malformed shared page-tree DAG causing resource exhaustion","summary":"Pillow is a Python imaging library. From 5.1.0 until 13.0.0, PdfParser.linearize_page_tree() in src/PIL/PdfParser.py treats a PDF /Pages graph as a tree without tracking duplicate indirect references. When Image.save(..., format=\"PDF\", a…","severity":"high","cvss":8.2,"cvssVector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N","cvssSource":"cna","cwe":["CWE-400","CWE-407"],"vendor":"python-pillow","product":"Pillow","affected":["Pillow >= 5.1.0, < 13.0.0"],"published":"2026-10-21","updated":"2026-10-21","sourceUpdated":"2026-10-21T21:03:22.785Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-96640","references":[{"url":"https://github.com/python-pillow/Pillow/security/advisories/GHSA-mrfp-p49p-3hf2","label":"https://github.com/python-pillow/Pillow/security/advisories/GHSA-mrfp-p49p-3hf2"},{"url":"https://github.com/python-pillow/Pillow/pull/10093","label":"https://github.com/python-pillow/Pillow/pull/10093"},{"url":"https://github.com/python-pillow/Pillow/commit/6f0e7ee1f9c2fe227906f8a4b926e6622b702bc7","label":"https://github.com/python-pillow/Pillow/commit/6f0e7ee1f9c2fe227906f8a4b926e6622b702bc7"},{"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":"2026-10-21T22:18:33.775Z","slug":"CVE-2026-96640","body":"## Overview\n\nPillow is a Python imaging library. From 5.1.0 until 13.0.0, PdfParser.linearize_page_tree() in src/PIL/PdfParser.py treats a PDF /Pages graph as a tree without tracking duplicate indirect references. When Image.save(..., format=\"PDF\", append=True) processes an attacker-controlled existing PDF whose /Kids arrays repeatedly reference the same child /Pages node, Pillow expands the shared subtree as distinct pages. A compact malformed PDF can therefore create exponentially many page references and consume disproportionate CPU before the append completes. This issue is fixed in version 13.0.0.\n\n## Affected\n\n- `Pillow >= 5.1.0, < 13.0.0`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"twilight","depthScore":45,"depthScoreParts":{"impact":45.1,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}