# CVE-2026-59200: python-pillow Pillow denial of service in PdfParser

Source: https://junglewise.ai/threats/cve-2026-59200-python-pillow-pillow-denial-of-service-in-pdfparser  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-14. Updated: 2026-07-20  
License: CC BY 4.0 with a link back

CVE-2026-59200 · Severity: high · CVSS 7.5 · Published 2026-07-14

Pillow, a popular Python library for image processing, contains a vulnerability in its PDF parsing component. An attacker can provide a specially crafted PDF file that, when opened, consumes massive amounts of server memory (a 'decompression bomb'). This can lead to a denial-of-service by crashing the application or slowing down the entire server, affecting all users.

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

## Quick answers

**Is CVE-2026-59200 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-59200 being exploited in the wild.

**How severe is CVE-2026-59200?** High severity, with a CVSS score of 7.5, published 14 July 2026.

**Which products and versions are affected?** pillow (PyPI) >= 5.1.0, < 12.3.0, ECOSYSTEM:introduced=5.1.0,fixed=12.3.0.

**Is there a fix for CVE-2026-59200?** 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-2026-59200 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-59200?** 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 vulnerability exists in `PdfParser.PdfStream.decode()` within `PdfParser.py`. The component calls `zlib.decompress()` using the PDF stream's 'Length' field as the `bufsize` parameter. In Python's zlib implementation, `bufsize` is only an initial buffer hint and does not enforce a maximum limit on the decompressed output. An attacker can craft a PDF with a FlateDecode-compressed stream that expands significantly (e.g., 1 GB from < 1 MB), leading to uncontrolled resource consumption (CWE-400). This is reachable when an application uses `PdfParser` to read untrusted PDF files. The issue is fixed in Pillow version 12.3.0.

## Affected products

- python-pillow Pillow >= 5.1.0, < 12.3.0

## Identifiers

- CVE-2026-59200
- GHSA-jjj6-mw9f-p565
- PYSEC-2026-3495

## Timeline

- 2026-07-07: patched: Fix released in version 12.3.0
- 2026-07-14: advisory: NVD publication date
- 2026-07-20: disclosed: GitHub Advisory published

## References

- [https://api.github.com/users/redyank](https://api.github.com/users/redyank)
- [https://github.com/redyank](https://github.com/redyank)
- [https://api.github.com/users/redyank/gists%7B/gist_id%7D](https://api.github.com/users/redyank/gists%7B/gist_id%7D)
- [https://api.github.com/users/redyank/repos](https://api.github.com/users/redyank/repos)
- [https://avatars.githubusercontent.com/u/96334924?v=4](https://avatars.githubusercontent.com/u/96334924?v=4)
- [https://api.github.com/users/redyank/events%7B/privacy%7D](https://api.github.com/users/redyank/events%7B/privacy%7D)

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