Resource exhaustion in Py-Pdf Pypdf
CVE-2026-22691
pypdf is a free and open-source pure-python PDF library. Prior to version 6.6.0, pypdf has possible long runtimes for malformed startxref. An attacker who uses this vulnerability can craft a PDF which leads to possibly long runtimes for invalid startxref entries. When rebuilding the cross-reference table, PDF files with lots of whitespace characters become problematic. Only the non-strict reading mode is affected. Only the non-strict reading mode is affected. This issue has been patched in version 6.6.0.
Vulnerability class: DoS (Denial of Service)
Published · last modified .
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: 0.004 (35.7th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 36th percentile — 35.7% 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: 0.004 · change: +0.000
Affected products
- Py-Pdf Pypdf — versions < 6.6.0
- Pypdf Project
Weakness classification (CWE)
References
- github.com/py-pdf/pypdf/security/advisories/GHSA-4f6g-68pf-7vhv (Mitigation, Vendor Advisory)
- github.com/py-pdf/pypdf/pull/3594 (Patch, Issue Tracking)
- github.com/py-pdf/pypdf/commit/294165726b646bb7799be1cc787f593f2fdbcf45 (Patch)
- github.com/py-pdf/pypdf/releases/tag/6.6.0 (Release Notes)
Frequently asked questions
- What is CVE-2026-22691?
- CVE-2026-22691 is a medium-severity vulnerability in Py-Pdf Pypdf, classified under Uncontrolled Resource Consumption. CVSS score: 5.3/10. Published 2026-01-10.
- How severe is CVE-2026-22691?
- Medium severity. CVSS v3 base score is 5.3 out of 10.