# CVE-2026-112891: Pillow quadratic copying in GIF comment handling

Source: https://junglewise.ai/threats/cve-2026-112891-pillow-is-a-python-imaging-library-from-9-2-0-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-2026-112891 · Severity: medium · CVSS 4 · Published 2026-10-19

Pillow is a Python library for image processing used in many web and server applications. When saving a GIF image with a very long comment, the library performs redundant repeated copying operations that consume excessive CPU time. An attacker can exploit this by providing a specially crafted GIF file with a large comment, potentially slowing down or crashing applications that process untrusted images.

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-2026-112891 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-112891 being exploited in the wild.

**How severe is CVE-2026-112891?** Medium severity, with a CVSS score of 4, published 19 October 2026.

**Which products and versions are affected?** pillow (PyPI) >= 9.2.0, < 13.0.0, ECOSYSTEM:introduced=9.2.0,fixed=13.0.0; Python Pillow Pillow 9.2.0 to 12.x (before 13.0.0).

**Is there a fix for CVE-2026-112891?** 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-2026-112891 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-112891?** 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 vulnerability exists in the _get_global_header() function in GifImagePlugin.py, which performs quadratic copying of comment data while assembling the GIF global header. This affects untrusted input images containing large comments. The attack requires only network access to supply a malicious GIF file and results in excessive CPU consumption leading to denial of service.

## Affected products

- Python Pillow Pillow 9.2.0 to 12.x (before 13.0.0)

## Identifiers

- CVE-2026-112891
- GHSA-fc9g-5qg7-mf45

## Timeline

- 2026-10-19: disclosed
- 2026-10-16: patched: Pillow 13.0.0 released

## 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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