{"id":"PYSEC-2026-4339","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.","aliases":["CVE-2026-96639","GHSA-v9pv-5gc8-w2m6"],"modified":"2026-10-28T11:00:02.232820278Z","published":"2026-10-21T21:20:32.217Z","references":[{"type":"ADVISORY","url":"https://github.com/python-pillow/Pillow/releases/tag/13.0.0"},{"type":"ADVISORY","url":"https://github.com/python-pillow/Pillow/security/advisories/GHSA-v9pv-5gc8-w2m6"},{"type":"REPORT","url":"https://github.com/python-pillow/Pillow/pull/10105"},{"type":"FIX","url":"https://github.com/python-pillow/Pillow/commit/78d97d994579aef81aafe123773d525f40f2522a"}],"affected":[{"package":{"name":"pillow","ecosystem":"PyPI","purl":"pkg:pypi/pillow"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"11.0.0"},{"fixed":"13.0.0"}]}],"versions":["11.0.0","11.1.0","11.2.1","11.3.0","12.0.0","12.1.0","12.1.1","12.2.0","12.3.0"],"ecosystem_specific":{},"database_specific":{"source":"https://github.com/pypa/advisory-database/blob/main/vulns/pillow/PYSEC-2026-4339.yaml"}}],"schema_version":"1.9.2","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"}]}