pypdf is a free and open-source pure-python PDF library. An attacker who uses a vulnerability present in versions prior to 6.10.1 can craft a PDF which leads to long runtimes. This requires cross-reference streams with wrong large `/Size` values or object streams with wrong large `/N` values. This has been fixed in pypdf 6.10.1. As a workaround, one may apply the changes from the patch manually.