# CVE-2026-96644: Pillow heap buffer over-read in WMF image handler on Windows

Source: https://junglewise.ai/threats/cve-2026-96644-pillow-is-a-python-imaging-library-prior-to-13-0-0-on-windows-src  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-21. Updated: 2026-10-21  
License: CC BY 4.0 with a link back

CVE-2026-96644 · Severity: high · CVSS 4 · Published 2026-10-21

Pillow is a Python image processing library used in web applications and data processing workflows. On Windows systems, a specially crafted WMF or EMF image file can trigger a heap buffer over-read in the image renderer, potentially exposing sensitive memory contents or crashing applications that process untrusted image files.

Technologies: [pillow (PyPI)](https://junglewise.ai/threats/technologies/pillow), [Python Pillow Pillow](https://junglewise.ai/threats/technologies/python-pillow-pillow). Vendors: [PyPI](https://junglewise.ai/threats/vendors/pypi), [Python Pillow](https://junglewise.ai/threats/vendors/python-pillow).

## Quick answers

**Is CVE-2026-96644 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-96644 being exploited in the wild.

**How severe is CVE-2026-96644?** High severity, with a CVSS score of 4, published 21 October 2026.

**Which products and versions are affected?** pillow (PyPI) < 13.0.0, ECOSYSTEM:introduced=0,fixed=13.0.0; Python Pillow Pillow prior to 13.0.0 on Windows.

**Is there a fix for CVE-2026-96644?** Yes. pillow (PyPI): upgrade to 13.0.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-96644 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-96644?** Check whether you run pillow (PyPI) or Python Pillow Pillow at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- pillow (PyPI): upgrade to 13.0.0 or later

  ```sh
  pip install "pillow>=13.0.0"
  ```


## Technical details

The WmfImagePlugin fails to validate full 32-bit WMF/EMF dimensions before passing them to the native Windows renderer, which truncates to 16-bit values for buffer allocation but uses the original full dimensions for pixel data copying. A crafted wide, short metafile bypasses the decompression-bomb check and causes out-of-bounds heap reads. This affects Windows deployments only and requires processing a malicious image file.

## Affected products

- Python Pillow Pillow prior to 13.0.0 on Windows

## Identifiers

- CVE-2026-96644
- BIT-PILLOW-2026-96644
- GHSA-9v9v-9qvf-h2hj
- PYSEC-2026-4343

## Timeline

- 2026-10-21: disclosed
- 2026-10-04: patched: fix merged to main branch

## References

- [https://github.com/python-pillow/Pillow/commit/4cf46bee338304c5c8968fd7f132ba0d40c428b7](https://github.com/python-pillow/Pillow/commit/4cf46bee338304c5c8968fd7f132ba0d40c428b7)
- [https://github.com/python-pillow/Pillow/pull/10120](https://github.com/python-pillow/Pillow/pull/10120)

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