CVE-2026-22691

low-risk

Published 2026-01-10

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.

Do I need to act?

0.02% chance of exploitation

EPSS score — low exploit probability

Not on CISA KEV list

No confirmed active exploitation reported to CISA

Patch status unknown

Check vendor advisories for fix availability and mitigation guidance

CVSS 5.3/10 Medium

NETWORK / LOW complexity

Affected Products (1)

Pypdf

Affected Vendors

Pypdf Project

References (4)

Patch https://github.com/py-pdf/pypdf/commit/294165726b646bb7799be1cc787f593f2fdbcf45

Issue Tracking https://github.com/py-pdf/pypdf/pull/3594

Release Notes https://github.com/py-pdf/pypdf/releases/tag/6.6.0

Vendor Advisory https://github.com/py-pdf/pypdf/security/advisories/GHSA-4f6g-68pf-7vhv

/ 100

low-risk

Severity 21/34 · High

Exploitability 0/34 · Minimal

Exposure 5/34 · Minimal