# CVE-2026-112401: Pillow quadratic copying in GIF comment parsing

Source: https://junglewise.ai/threats/cve-2026-112401-pillow-is-a-python-imaging-library-from-5-4-0-until-13-0-0  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-19. Updated: 2026-10-19  
License: CC BY 4.0 with a link back

CVE-2026-112401 · Severity: medium · CVSS 4 · Published 2026-10-19

Pillow is a Python image processing library used by applications to open and manipulate image files. A flaw in how it parses GIF comment metadata causes it to perform wasteful repeated copying operations. An attacker can create a malicious GIF file with many comment blocks that forces the application to consume excessive CPU when opening the file, potentially causing a denial of service.

Technologies: [pillow (PyPI)](https://junglewise.ai/threats/technologies/pillow), [Python Pillow Pillow](https://junglewise.ai/threats/technologies/python-pillow-pillow). Vendors: [PyPI](https://junglewise.ai/threats/vendors/pypi), [Python Pillow](https://junglewise.ai/threats/vendors/python-pillow).

## Quick answers

**Is CVE-2026-112401 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-112401 being exploited in the wild.

**How severe is CVE-2026-112401?** Medium severity, with a CVSS score of 4, published 19 October 2026.

**Which products and versions are affected?** pillow (PyPI) >= 5.4.0, < 13.0.0, ECOSYSTEM:introduced=5.4.0,fixed=13.0.0; Python Pillow Pillow 5.4.0 through 12.x.

**Is there a fix for CVE-2026-112401?** 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-2026-112401 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-112401?** 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

  ```sh
  pip install "pillow>=13.0.0"
  ```


## Technical details

The GifImagePlugin._seek() method in Pillow 5.4.0 through 12.x repeatedly concatenates immutable bytes objects when parsing GIF comment extensions, resulting in quadratic time complexity. Frame zero is parsed during Image.open(), triggering the vulnerability without requiring further image operations. An attacker can supply a small-dimension GIF with multiple comment extensions to exhaust CPU resources and deny service.

## Affected products

- python-pillow Pillow 5.4.0 through 12.x

## Identifiers

- CVE-2026-112401
- GHSA-74r2-7ff9-mjj2

## Timeline

- 2026-10-19: disclosed
- 2026-10-16: patched: Fixed in Pillow 13.0.0 release

## References

- [https://github.com/python-pillow/Pillow/commit/68a3fe957d8a4d552e8c69d96066d749f0614c7e](https://github.com/python-pillow/Pillow/commit/68a3fe957d8a4d552e8c69d96066d749f0614c7e)
- [https://github.com/python-pillow/Pillow/releases/tag/13.0.0](https://github.com/python-pillow/Pillow/releases/tag/13.0.0)

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