An attacker who uses this vulnerability can craft a PDF which leads to large runtimes/memory usage. This requires accessing the page count of an encrypted PDF file, which itself declares a wrong /Count value.
This has been fixed in pypdf==6.21.3.
If you cannot upgrade yet, consider applying the changes from PR #4270.
{
"cwe_ids": [
"CWE-400",
"CWE-770"
],
"github_reviewed": true,
"github_reviewed_at": "2026-10-30T23:08:24Z",
"nvd_published_at": "2026-10-29T21:17:20Z",
"severity": "HIGH"
}