What’s Vulnerable › Vulnerabilities

CVE-2026-96638: Pillow: BMP RLE decoder memory-amplification DoS via unbounded delta escape / absolute mode

• Severity: medium (CVSS 6.5 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: none known
• Published: 2026-10-21 · updated 2026-10-28
• Weakness: CWE-400

Description

Pillow is a Python imaging library. From 9.1.0 until 13.0.0, BmpRleDecoder.decode() in src/PIL/BmpImagePlugin.py permits crafted RLE BMP delta escapes and absolute-mode runs to append beyond the remaining dest_length without a per-branch cap. A delta can add roughly 255 image rows in one iteration, so a kilobyte-sized file with a large but permitted width can expand the data bytearray to hundreds of megabytes or more, causing memory-exhaustion denial of service. This issue is fixed in version 13.0.0.

Affected products

• python-pillow Pillow: from 9.1.0 before 13.0.0 — fixed in 13.0.0
• python-pillow Pillow: from 9.1.0, < 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/e7794835e323ff2691d9b3a974cade1a44301b9a
• https://github.com/python-pillow/Pillow/pull/10015
• https://github.com/python-pillow/Pillow/releases/tag/13.0.0
• https://github.com/python-pillow/Pillow/security/advisories/GHSA-24rc-8hj2-v98c

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