CVE-2026-96640

HIGH

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.

CVSS v3.1 Score

7.5
HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Published: 10/21/2026Modified: 10/28/2026

Related Intelligence (1)

HIGHVulnerability

NVD HIGH: CVE-2026-96640 — Pillow is a Python imaging library. From 5.1.0 until 13.0.0, PdfParser.linearize...

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

CVE-2026-96640
NIST NVD

References (5)

https://github.com/python-pillow/Pillow/commit/6f0e7ee1f9c2fe227906f8a4b926e6622b702bc7Patchhttps://github.com/python-pillow/Pillow/pull/10093Issue Trackinghttps://github.com/python-pillow/Pillow/releases/tag/13.0.0Release Noteshttps://github.com/python-pillow/Pillow/security/advisories/GHSA-mrfp-p49p-3hf2Vendor Advisoryhttps://github.com/python-pillow/Pillow/security/advisories/GHSA-mrfp-p49p-3hf2Vendor Advisory