Vulnerability · Published Oct 21, 2026 · Assigned by GitHub_M
CVE-2026-96639Pillow multi-frame loaders can reuse stale native image storage after mode transitions
Critical 9.8
In plain English
A critical-severity out-of-bounds read in Pillow from python-pillow. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.7% (higher than 52% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | pillow | no fix listed | DEBIAN-CVE-2026-96639 |
| Debian:13 | pillow | no fix listed | DEBIAN-CVE-2026-96639 |
| Debian:14 | pillow | no fix listed | DEBIAN-CVE-2026-96639 |
| PyPI | pillow | 13.0.0 | PYSEC-2026-4339 |
| PyPI | pillow | 13.0.0 | GHSA-v9pv-5gc8-w2m6 |
| Ubuntu:26.04:LTS | pillow | no fix listed | UBUNTU-CVE-2026-96639 |
| Ubuntu:26.10 | pillow | no fix listed | UBUNTU-CVE-2026-96639 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| python-pillow | Pillow | >= 11.0.0, < 13.0.0 |
Weakness: CWE-125, CWE-787 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
References
- https://github.com/python-pillow/Pillow/security/advisories/GHSA-v9pv-5gc8-w2m6 x_refsource_CONFIRM
- https://github.com/python-pillow/Pillow/pull/10105 x_refsource_MISC
- https://github.com/python-pillow/Pillow/commit/78d97d994579aef81aafe123773d525f40f2522a x_refsource_MISC
- https://github.com/python-pillow/Pillow/releases/tag/13.0.0 x_refsource_MISC