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pypdf Denial of Service via Crafted Cross-Reference Stream

A security vulnerability in pypdf allows crafted PDFs with cross-reference streams using /W [0 0 0] and large /Size values to cause long runtimes, leading to po

13 Jun 2026Read 1 minSeverity: schedule it

What changed

A security vulnerability in pypdf allows crafted PDFs with cross-reference streams using /W [0 0 0] and large /Size values to cause long runtimes, leading to potential denial of service.

Who it affects

All users of pypdf prior to version 6.12.0 who process untrusted PDF files.

What to do today

Upgrade to pypdf==6.12.0 or apply the changes from PR #3791 if immediate upgrade is not possible.

The trail
Collected Audited Written Published