CVE-2026-96639: python-pillow pillow Out-of-bounds Read

Vulnerability summary

CVE-2026-96639 is a critical (CVSS 9.8) Out-of-bounds Read vulnerability in python-pillow pillow.

Timeline

1. 21-10-2026
   PublishedVulnerability first disclosed.

Description

Pillow is a Python imaging library. From 11.0.0 until 13.0.0, multi-frame loaders can retain an ImagingCore allocation created for a narrow frame mode while a later frame of the same dimensions changes the logical mode and decoder tiles to wider RGB or CMYK data. ImageFile.load_prepare() reuses the stale native storage because _im is non-null without verifying that its mode and size still match. Crafted PSD, MPO, DCX, or MIC frame transitions can then write wider pixels into the narrow allocation, causing native out-of-bounds writes and crashes. The MPO path can also cause a native over-read and, in demonstrated runtime-specific profiles, command execution. This issue is fixed in version 13.0.0.

• CWE-125Out-of-bounds ReadThe product reads data past the end, or before the beginning, of the intended buffer.
• CWE-787Out-of-bounds WriteThe product writes data past the end, or before the beginning, of the intended buffer.