CVE-2026-96639: pillow Out-of-bounds Read — Fix

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.

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CVSS v3.1 Score

9.8

CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS — Exploit Prediction

0.0067

Probability of exploitation

0.52%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-125 Out-of-bounds Read

CWE-787 Out-of-bounds Write

Affected Products

Vendor	Product	Versions
python	pillow	11.0.0 — 13.0.0

References

Advisories & Patches

https://github.com/python-pillow/Pillow/commit/78d97d994579aef81aafe123773d525f40f2522a https://github.com/python-pillow/Pillow/security/advisories/GHSA-v9pv-5gc8-w2m6

Other References

https://github.com/python-pillow/Pillow/pull/10105 https://github.com/python-pillow/Pillow/releases/tag/13.0.0

Frequently Asked Questions

What is CVE-2026-96639? +

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. It has a CVSS v3.1 base score of 9.8 (CRITICAL).

How severe is CVE-2026-96639? +

CVE-2026-96639 has a CVSS v3.1 score of 9.8 out of 10, rated CRITICAL. This is a critical vulnerability that should be patched immediately. The EPSS score is 0.0067, placing it in the 1th percentile for exploitation probability.

What products are affected by CVE-2026-96639? +

CVE-2026-96639 affects products from python, specifically: pillow. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-96639? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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