CVE-2026-96644 Pillow: Heap over-read in WMF/EMF rendering via 16-bit dimension truncation (Windows builds)

What is CVE-2026-96644?

CVE-2026-96644 is a high-severity vulnerability in Python Pillow, published on 21 Oct 2026.

Official description

Pillow is a Python imaging library. Prior to 13.0.0 on Windows, src/PIL/WmfImagePlugin.py passes unchecked 32-bit WMF or EMF dimensions to the native drawwmf handler in src/display.c. The handler sizes a DIB allocation from 16-bit-truncated bcWidth and bcHeight fields but copies pixel data using the original full dimensions. A crafted wide, short metafile can pass the pixel-count decompression-bomb check and make the Windows-only renderer read beyond the heap buffer, potentially disclosing memory or crashing the process. This issue is fixed in version 13.0.0.

Weakness: CWE-125

Which versions are affected by CVE-2026-96644?

4 open source packages ship an affected version, including pillow and Pillow. It affects 1 product.

Products include Python Pillow.

How do I fix CVE-2026-96644?

Upgrade pillow to 13.0.0 or later.

Is CVE-2026-96644 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-96644 exists.

Other vulnerabilities in Python Pillow

• CVE-2014-3007 Pillow command injection Critical 10.0
• CVE-2026-96639 Pillow multi-frame loaders can reuse stale native image storage after mode transitions Critical 9.8
• CVE-2022-30595 Buffer over-flow in Pillow Critical 9.8
• CVE-2021-25289 Out of bounds write in Pillow Critical 9.8
• CVE-2016-4009 Pillow Integer overflow in ImagingResampleHorizontal Critical 9.8

All Python Pillow vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as BIT-pillow-2026-96644, CLSA-2026-1793189478, ECHO-5bbc-7f9f-d028, GHSA-9v9v-9qvf-h2hj, PYSEC-2026-4343, ROOT-APP-PYPI-CVE-2026-96644 and 1 more.