An attacker who uses this vulnerability can craft a PDF which leads to long runtimes. This requires loading relevant parts of a file (like their pages) where the same, but non-existent indirect object is referenced multiple times.
This has been fixed in pypdf==6.21.2.
If you cannot upgrade yet, consider applying the changes from PR #4240.
{
"cwe_ids": [
"CWE-400"
],
"github_reviewed": true,
"github_reviewed_at": "2026-10-23T20:55:15Z",
"nvd_published_at": null,
"severity": "HIGH"
}