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CVE-2026-112402: Pillow: Double free in ImagingScaleAffine on calloc failure via Image.transform

• 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: yes
• Published: 2026-10-19 · updated 2026-10-27
• Weakness: CWE-416

Description

Pillow is a Python imaging library. Prior to 13.0.0, Pillow can double free image memory when ImagingScaleAffine encounters a selective allocation failure. The affected fast path handles Transform.EXTENT or pure scale-and-translate Transform.AFFINE operations with the default NEAREST resampling. The output image allocation must succeed while the additional per-column lookup allocation fails, after which the error path deletes image storage that later cleanup releases again. An attacker who can drive such a large Image.transform() operation under memory pressure may trigger the failure. This can crash the process and may corrupt memory. This issue is fixed in version 13.0.0.

Affected products

• python-pillow Pillow: before 13.0.0 — fixed in 13.0.0
• Pypi Pillow: before 13.0.0; 1.0, 1.1, 1.2, 1.3, 1.4, 1.5 (+101) — fixed in 13.0.0
• python-pillow Pillow: before 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

• https://github.com/python-pillow/Pillow/commit/aafa6c75f7cdabb9f409a8aac7c780bea31d08d9
• https://github.com/python-pillow/Pillow/releases/tag/13.0.0
• https://github.com/python-pillow/Pillow/security/advisories/GHSA-7mwm-ghpf-9vrm
• https://github.com/python-pillow/Pillow/security/advisories/GHSA-7mwm-ghpf-9vrm

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