An attacker who uses this vulnerability can craft a PDF which leads to large memory consumption. This requires parsing the /ToUnicode entry of a font with unusually large values, for example during text extraction.
This has been fixed in pypdf==6.18.1.
If you cannot upgrade yet, consider applying the changes from PR #4071.
{
"cwe_ids": [
"CWE-400"
],
"github_reviewed": true,
"github_reviewed_at": "2026-10-01T15:06:04Z",
"nvd_published_at": "2026-09-30T21:17:06Z",
"severity": "HIGH"
}