Quick answers
- Is CVE-2026-96639 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-96639 being exploited in the wild.
- How severe is CVE-2026-96639?
- Critical severity, with a CVSS score of 9.8, published 21 October 2026.
- Which products and versions are affected?
- pillow (PyPI) >= 11.0.0, < 13.0.0, ECOSYSTEM:introduced=11.0.0,fixed=13.0.0; Python Pillow Pillow 11.0.0 to 12.x.
- Is there a fix for CVE-2026-96639?
- Yes. pillow (PyPI): upgrade to 13.0.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-96639 attacked?
- It is attacked over the network, in a software library.
- Am I affected by CVE-2026-96639?
- Check whether you run pillow (PyPI) or Python Pillow Pillow at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
How to fix
- pillow (PyPI): upgrade to 13.0.0 or later
pip install "pillow>=13.0.0"
Technical details
The vulnerability exists in ImageFile.load_prepare(), which reuses a stale ImagingCore allocation without verifying that the frame's mode and size match the previously allocated buffer. When a multi-frame file transitions to a frame with wider color data (RGB or CMYK from a narrower mode) while keeping the same dimensions, the decoder writes wider pixels into the undersized allocation, causing out-of-bounds writes. The MPO format path can also trigger native over-reads, leading to potential code execution in certain runtime contexts.
Affected products
- Python Pillow Pillow 11.0.0 to 12.x
Identifiers
- CVE-2026-96639
- BIT-PILLOW-2026-96639
- GHSA-v9pv-5gc8-w2m6
- PYSEC-2026-4339
Timeline
- 2026-10-21: disclosed
- 2026-10-03: patched: Fix committed but released in version 13.0.0