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PYSEC-2026-3018

pypdf: Possible infinite loop when processing threads/articles in writer

Quick fix

PYSEC-2026-3018 — pypdf: upgrade to the fixed version with the command below.

pip install --upgrade 'pypdf>=6.13.1'

Details

### Impact

An attacker who uses this vulnerability can craft a PDF which leads to an infinite loop. This requires merging a file with threads/articles into a writer.

### Patches

This has been fixed in [pypdf==6.13.1](https://github.com/py-pdf/pypdf/releases/tag/6.13.1).

### Workarounds

If users cannot upgrade yet, consider applying the changes from PR [#3839](https://github.com/py-pdf/pypdf/pull/3839).

Are you affected?

Enter the version of the package you're using.

Affected packages

PyPI/pypdf

Introduced in: 0Fixed in: 6.13.1

Fixpip install --upgrade 'pypdf>=6.13.1'

References

https://github.com/py-pdf/pypdf/security/advisories/GHSA-g9xf-7f8q-9mcj[WEB]
https://nvd.nist.gov/vuln/detail/CVE-2026-54651[ADVISORY]
https://github.com/py-pdf/pypdf/pull/3839[WEB]
https://github.com/py-pdf/pypdf[PACKAGE]
https://github.com/py-pdf/pypdf/releases/tag/6.13.1[WEB]
https://pypi.org/project/pypdf[PACKAGE]
https://github.com/advisories/GHSA-g9xf-7f8q-9mcj[ADVISORY]