An attacker who uses this vulnerability can craft a PDF which leads to long runtimes. This requires updating form field values with flattening enabled, which triggers appearance stream generation.
This has been fixed in pypdf==6.19.0.
If you cannot upgrade yet, consider applying the changes from PR #4087.
{
"cwe_ids": [
"CWE-400"
],
"github_reviewed": true,
"github_reviewed_at": "2026-10-01T15:07:21Z",
"nvd_published_at": "2026-09-30T21:17:07Z",
"severity": "HIGH"
}