What is CVE-2026-54651?

CVE-2026-54651 is a medium-severity vulnerability in Py-Pdf Pypdf, classified under Loop with Unreachable Exit Condition (Infinite Loop). CVSS score: 5.5/10. Published 2026-06-22.

How severe is CVE-2026-54651?

Medium severity. CVSS v3 base score is 5.5 out of 10.

Vulnerability in Py-Pdf Pypdf

CVE-2026-54651

pypdf is a free and open-source pure-python PDF library. Prior to 6.13.1, an attacker who uses this vulnerability can craft a PDF which leads to an infinite loop. This requires merging a file with threads/articles into a writer. This vulnerability is fixed in 6.13.1.

Published 2026-06-22 · last modified 2026-06-24.

CVSS v3 metric

CVSS v3 base score 5.5 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.002 (5.4th percentile), scored 2026-09-23.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 5th percentile — 5.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: 0.000

Affected products

Py-Pdf Pypdf — versions < 6.13.1
Pypdf Project

Weakness classification (CWE)

CWE-835 — Loop with Unreachable Exit Condition (Infinite Loop)

References

github.com/py-pdf/pypdf/security/advisories/GHSA-g9xf-7f8q-9mcj (Patch, Mitigation, Vendor Advisory)
github.com/py-pdf/pypdf/pull/3839 (Issue Tracking)
github.com/py-pdf/pypdf/releases/tag/6.13.1 (Patch)

Frequently asked questions

What is CVE-2026-54651?: CVE-2026-54651 is a medium-severity vulnerability in Py-Pdf Pypdf, classified under Loop with Unreachable Exit Condition (Infinite Loop). CVSS score: 5.5/10. Published 2026-06-22.
How severe is CVE-2026-54651?: Medium severity. CVSS v3 base score is 5.5 out of 10.