CVE-2026-96640

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", 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.

• CWE-400
• CWE-407

• https://github.com/python-pillow/Pillow/commit/6f0e7ee1f9c2fe227906f8a4b926e6622b702bc7Patch
• https://github.com/python-pillow/Pillow/pull/10093Issue Tracking
• https://github.com/python-pillow/Pillow/releases/tag/13.0.0Release Notes
• https://github.com/python-pillow/Pillow/security/advisories/GHSA-mrfp-p49p-3hf2Vendor Advisory
• https://github.com/python-pillow/Pillow/security/advisories/GHSA-mrfp-p49p-3hf2Vendor Advisory

Published

Oct 21, 2026

Last Modified

Oct 28, 2026

Status

Modified

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
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