Low severityOSV Advisory· Published Jan 10, 2026· Updated Jan 12, 2026
pypdf has possible long runtimes for malformed startxref
CVE-2026-22691
Description
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.
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Affected packages
Versions sourced from the GitHub Security Advisory.
| Package | Affected versions | Patched versions |
|---|---|---|
pypdfPyPI | < 6.6.0 | 6.6.0 |
Affected products
4- osv-coords3 versions
< 0.7.2-r0+ 2 more
- (no CPE)range: < 0.7.2-r0
- (no CPE)range: < 0.7.2-r0
- (no CPE)range: < 6.6.0
Patches
Vulnerability mechanics
References
6- github.com/advisories/GHSA-4f6g-68pf-7vhvghsaADVISORY
- nvd.nist.gov/vuln/detail/CVE-2026-22691ghsaADVISORY
- github.com/py-pdf/pypdf/commit/294165726b646bb7799be1cc787f593f2fdbcf45ghsax_refsource_MISCWEB
- github.com/py-pdf/pypdf/pull/3594ghsax_refsource_MISCWEB
- github.com/py-pdf/pypdf/releases/tag/6.6.0ghsax_refsource_MISCWEB
- github.com/py-pdf/pypdf/security/advisories/GHSA-4f6g-68pf-7vhvghsax_refsource_CONFIRMWEB
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