pypdf has possible long runtimes/large memory usage for large /ToUnicode streams

Impact

An attacker who uses this vulnerability can craft a PDF which leads to long runtimes and large memory consumption. This requires parsing the /ToUnicode entry of a font with unusually large values, for example during text extraction.

Patches

This has been fixed in pypdf==6.7.1.

Workarounds

If you cannot upgrade yet, consider applying the changes from PR #3646.