pypdf: Possible long runtimes for repeated malformed cross-reference entries (Follow-up)

Impact

An attacker who uses this vulnerability can craft a PDF which leads to long runtimes. This requires cross-reference streams with repeated malformed cross-reference streams.

Patches

This has been fixed in pypdf==6.21.2.

Workarounds

If you cannot upgrade yet, consider applying the changes from PR #4240.

Notes

This is a follow-up to https://github.com/py-pdf/pypdf/security/advisories/GHSA-55h5-xmcq-c37v, which had the side-effect of still loading the whole stream again despite the cache being present.