What is CVE-2026-28804?

CVE-2026-28804 is a medium-severity vulnerability in Py-Pdf Pypdf, classified under Inefficient Algorithmic Complexity. CVSS score: 5.3/10. Published 2026-03-06.

How severe is CVE-2026-28804?

Medium severity. CVSS v3 base score is 5.3 out of 10.

Vulnerability in Py-Pdf Pypdf

CVE-2026-28804

pypdf is a free and open-source pure-python PDF library. Prior to version 6.7.5, an attacker who uses this vulnerability can craft a PDF which leads to long runtimes. This requires accessing a stream which uses the /ASCIIHexDecode filter. This issue has been patched in version 6.7.5.

Published 2026-03-06 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L.

EPSS exploit prediction

EPSS: 0.005 (41.6th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 42nd percentile — 41.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.004 · newest: 0.005 · change: +0.001

Affected products

Py-Pdf Pypdf — versions < 6.7.5
Pypdf Project

Weakness classification (CWE)

CWE-407 — Inefficient Algorithmic Complexity

References

github.com/py-pdf/pypdf/security/advisories/GHSA-9m86-7pmv-2852 (Patch, Vendor Advisory)
github.com/py-pdf/pypdf/pull/3666 (Patch, Issue Tracking)
github.com/py-pdf/pypdf/commit/648c627d2657447dfb1773412af05a0a5103b98f (Patch)
github.com/py-pdf/pypdf/releases/tag/6.7.5 (Product, Release Notes)

Frequently asked questions

What is CVE-2026-28804?: CVE-2026-28804 is a medium-severity vulnerability in Py-Pdf Pypdf, classified under Inefficient Algorithmic Complexity. CVSS score: 5.3/10. Published 2026-03-06.
How severe is CVE-2026-28804?: Medium severity. CVSS v3 base score is 5.3 out of 10.