BIT-pillow-2026-96639

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BIT-pillow-2026-96639

Summary: Pillow multi-frame loaders can reuse stale native image storage after mode transitions

Details: 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.

References: https://github.com/python-pillow/Pillow/commit/78d97d994579aef81aafe123773d525f40f2522a, https://github.com/python-pillow/Pillow/pull/10105, https://github.com/python-pillow/Pillow/releases/tag/13.0.0, https://github.com/python-pillow/Pillow/security/advisories/GHSA-v9pv-5gc8-w2m6, https://nvd.nist.gov/vuln/detail/CVE-2026-96639