CVE-2026-112895: Pillow: Unbounded recursion parsing a PDF page tree or trailer chain (incomplete fix for CVE-2026-42310)

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-10-19 · updated 2026-10-27
Weakness: CWE-674

Description

Pillow is a Python imaging library. From 5.1.0 until 13.0.0, Pillow can exhaust resources while parsing an existing PDF during an append operation. PdfParser follows page-tree child references without cycle or duplication tracking and follows previous-trailer chains with only an exact repeated-offset guard, so deep or cyclic page trees and long chains of unique trailer offsets can exhaust the Python stack. Repeated non-cyclic /Kids references can also cause super-linear CPU and memory use. An attacker can supply such a PDF to an application that calls Image.save with PDF append enabled. This can raise an uncaught RecursionError or consume excessive CPU and memory before output is written, causing denial of service. This issue is fixed in version 13.0.0.

Affected products

python-pillow Pillow: from 5.1.0 before 13.0.0 — fixed in 13.0.0
Pypi Pillow: from 5.1.0 before 13.0.0; 10.0.0, 10.0.1, 10.1.0, 10.2.0, 10.3.0, 10.4.0 (+43) — fixed in 13.0.0
python-pillow Pillow: from 5.1.0, < 13.0.0

How to fix

Upgrade to a fixed version: python-pillow Pillow 13.0.0; Pypi Pillow 13.0.0. Check the vendor advisory for mitigations.

References

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