An attacker who uses this vulnerability can craft a PDF which leads to large memory usage. This requires parsing a content stream with a rather large /Length value, regardless of the actual data length inside the stream.
This has been fixed in pypdf==6.8.0.
If you cannot upgrade yet, consider applying the changes from PR #3675.
As far as we are aware, this mostly affects reading from buffers of unknown size, as returned by open("file.pdf", mode="rb") for example. Passing a file path or a BytesIO buffer to pypdf instead does not seem to trigger the vulnerability.
{
"nvd_published_at": "2026-03-10T22:16:20Z",
"github_reviewed_at": "2026-03-11T00:14:02Z",
"cwe_ids": [
"CWE-770"
],
"severity": "MODERATE",
"github_reviewed": true
}