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PYSEC-2026-1827

pypdf has possible Infinite Loop when processing outlines/bookmarks

Quick fix

PYSEC-2026-1827 — pypdf: upgrade to the fixed version with the command below.

pip install --upgrade 'pypdf>=6.6.2'

Details

### Impact

An attacker who uses this vulnerability can craft a PDF which leads to an infinite loop. This requires accessing the outlines/bookmarks.

### Patches

This has been fixed in [pypdf 6.6.2](https://github.com/py-pdf/pypdf/releases/tag/6.6.2).

### Workarounds

If projects cannot upgrade yet, consider applying the changes from PR [#3610](https://github.com/py-pdf/pypdf/pull/3610).

Are you affected?

Enter the version of the package you're using.

Affected packages

PyPI/pypdf
Introduced in: 0Fixed in: 6.6.2
Fixpip install --upgrade 'pypdf>=6.6.2'

References