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pypdf FlateDecode PNG Predictor DoS Vulnerability

A vulnerability in pypdf allows an attacker to craft a PDF that leads to long runtimes when accessing a stream using the /FlateDecode filter with a PNG predictor.

17 Jun 2026Read 1 minSeverity: schedule it

What changed

A vulnerability in pypdf allows an attacker to craft a PDF that leads to long runtimes when accessing a stream using the /FlateDecode filter with a PNG predictor. Fixed in pypdf 6.12.2.

Who it affects

Users of pypdf who process untrusted PDF files, especially those using /FlateDecode with PNG predictors.

What to do today

Upgrade to pypdf 6.12.2 or apply the changes from PR #3806.

The trail
Collected Audited Written Published