# CVE-2026-55380: Pillow heap allocation overflow in GdImageFile decompression bomb check

Source: https://junglewise.ai/threats/cve-2026-55380-pillow-heap-allocation-overflow-in-gdimagefile-decompression-bomb  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-06. Updated: 2026-07-20  
License: CC BY 4.0 with a link back

CVE-2026-55380 · Severity: high · CVSS 7.5 · Published 2026-07-06

Pillow, a popular Python library for image processing, contains a vulnerability in how it handles GD 2.x image files. An attacker can provide a specially crafted, very small image file (about 1KB) that forces the library to attempt to allocate over 4GB of memory. This can lead to a denial-of-service condition where the application crashes or becomes unresponsive due to memory exhaustion.

Technologies: [pillow (PyPI)](https://junglewise.ai/threats/technologies/pillow). Vendors: [PyPI](https://junglewise.ai/threats/vendors/pypi).

## Quick answers

**Is CVE-2026-55380 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-55380 being exploited in the wild.

**How severe is CVE-2026-55380?** High severity, with a CVSS score of 7.5, published 6 July 2026.

**Which products and versions are affected?** pillow (PyPI) < 12.3.0, ECOSYSTEM:introduced=0,fixed=12.3.0.

**Is there a fix for CVE-2026-55380?** Yes. pillow (PyPI): upgrade to 12.3.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-55380 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-55380?** Check whether you run pillow (PyPI) 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 12.3.0 or later

  ```sh
  pip install "pillow>=12.3.0"
  ```


## Technical details

The GdImageFile plugin in Pillow does not call Image._decompression_bomb_check() during its _open() method. Because this plugin is not registered with the standard Image.register_open() system and is instead accessed via its own entry point (PIL.GdImageFile.open), it bypasses the library's global protection against decompression bombs. An attacker can craft a GD 2.x header (1,037 bytes) specifying maximum dimensions (65535x65535), which triggers a ~4.3 GB C-level heap allocation when load() is called. This exceeds the default DecompressionBombError threshold by approximately 24 times. The issue is fixed in Pillow version 12.3.0.

## Affected products

- python-pillow Pillow < 12.3.0

## Identifiers

- CVE-2026-55380
- GHSA-phj9-mv4w-65pm
- PYSEC-2026-2256

## Timeline

- 2026-06-08: disclosed: Confirmed unpatched on main branch
- 2026-07-03: advisory: GitHub Advisory published
- 2026-07-06: kev added: NVD publication date
- 2026-07-20: patched: Updated in GitHub Advisory Database with patch version 12.3.0

## References

- [https://api.github.com/users/x-forwarded-sudo](https://api.github.com/users/x-forwarded-sudo)
- [https://github.com/x-forwarded-sudo](https://github.com/x-forwarded-sudo)
- [https://api.github.com/users/x-forwarded-sudo/gists%7B/gist_id%7D](https://api.github.com/users/x-forwarded-sudo/gists%7B/gist_id%7D)
- [https://api.github.com/users/x-forwarded-sudo/repos](https://api.github.com/users/x-forwarded-sudo/repos)
- [https://avatars.githubusercontent.com/u/223256873?v=4](https://avatars.githubusercontent.com/u/223256873?v=4)
- [https://api.github.com/users/x-forwarded-sudo/events%7B/privacy%7D](https://api.github.com/users/x-forwarded-sudo/events%7B/privacy%7D)

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