# CVE-2026-112399: Pillow APNG decompression bomb denial of service

Source: https://junglewise.ai/threats/cve-2026-112399-pillow-is-a-python-imaging-library-from-8-1-0-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-2026-112399 · Severity: high · CVSS 4 · Published 2026-10-19

Pillow is a Python library for image processing. A crafted APNG (animated PNG) image file can trigger excessive memory allocation during image opening, bypassing safety checks meant to prevent such attacks. An attacker can create a malicious image that causes memory exhaustion and denial of service on systems processing untrusted image files.

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-2026-112399 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-112399 being exploited in the wild.

**How severe is CVE-2026-112399?** High severity, with a CVSS score of 4, published 19 October 2026.

**Which products and versions are affected?** pillow (PyPI) >= 8.1.0, < 13.0.0, ECOSYSTEM:introduced=8.1.0,fixed=13.0.0; Python Pillow Pillow 8.1.0 to 12.x.x (before 13.0.0).

**Is there a fix for CVE-2026-112399?** 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-2026-112399 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-112399?** 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 PNG image handling code where full-canvas memory allocation for APNG disposal backgrounds occurs before the decompression-bomb check is applied. A crafted APNG with a small first frame, a very large declared canvas size, and background disposal or OP_PREVIOUS operation triggers the over-allocation when Image.open() positions frame zero, without requiring pixel loading or frame iteration. This allows memory exhaustion and denial of service.

## Affected products

- Python Pillow Pillow 8.1.0 to 12.x.x (before 13.0.0)

## Identifiers

- CVE-2026-112399
- GHSA-5xm2-6676-qcp9

## Timeline

- 2026-10-19: disclosed
- 2026-10-16: patched: Fixed in version 13.0.0

## References

- [https://github.com/python-pillow/Pillow/commit/f1acfc54c53502948d0d14121872061df931db48](https://github.com/python-pillow/Pillow/commit/f1acfc54c53502948d0d14121872061df931db48)
- [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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- [Pillow memory denial of service in TIFF and EXIF parsing](https://junglewise.ai/threats/cve-2026-128066-pillow-memory-dos-in-tiff-and-exif-ifd-parsing-via-overlapping)
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