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CVE-2026-112891: Pillow: Quadratic GIF comment copying during save

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-19 · updated 2026-10-27
• Weakness: CWE-407

Description

Pillow is a Python imaging library. From 9.2.0 until 13.0.0, Pillow performs quadratic copying when saving a GIF with a long comment. _get_global_header() repeatedly copies portions of comment data while assembling the global header, including comments retained from an untrusted input image. An attacker can supply an image with a large GIF comment to an application that saves it as GIF. This can consume excessive CPU and delay or deny service. This issue is fixed in version 13.0.0.

Affected products

• python-pillow Pillow: from 9.2.0 before 13.0.0 — fixed in 13.0.0
• python-pillow Pillow: from 9.2.0, < 13.0.0

How to fix

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

References

• https://github.com/python-pillow/Pillow/commit/68a3fe957d8a4d552e8c69d96066d749f0614c7e
• https://github.com/python-pillow/Pillow/releases/tag/13.0.0
• https://github.com/python-pillow/Pillow/security/advisories/GHSA-fc9g-5qg7-mf45

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