Pillow: Quadratic GIF comment copying during save

ALTO 7.5CVE-2026-112891 · BIT-pillow-2026-112891 · GHSA-fc9g-5qg7-mf45 · Published 19/10/2026 · updated 27/10/2026

Package	Affected versions	Patched versions
pillow PyPI	`≥ 9.2.0, < 13.0.0`	`13.0.0`
pillow python	`≥ 9.2.0, < 13.0.0`	`13.0.0`

Description

On Pillow 12.3.0 and upstream main (ad277e2761b489681e71b51e91367d46b0ceabb9), a GIF with a long comment makes _get_global_header() copy portions of the comment repeatedly when saving, including comments carried over from untrusted images. I suggest provisional Moderate severity for crafted-image CPU denial of service, with CVSS-B 6.9 assuming a network service automatically opens unauthenticated uploads and they are resaved as GIFs; impact depends on input-size, concurrency, and worker CPU limits.

NVD 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.

References

python-pillow/Pillow security advisory · WEB
nvd.nist.gov/vuln/detail/CVE-2026-112891 · ADVISORY
python-pillow/Pillow commit 68a3fe9 · WEB
python-pillow/Pillow · PACKAGE
python-pillow/Pillow release 13.0.0 · WEB

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Package

Affected versions

Patched versions

pillow

PyPI

≥ 9.2.0, < 13.0.0

13.0.0

pillow

python

≥ 9.2.0, < 13.0.0

13.0.0

Description

NVD description