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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Fixes

Solution

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Workaround

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History

Sat, 10 Jan 2026 05:00:00 +0000

Type Values Removed Values Added
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.
Title pypdf has possible long runtimes for malformed startxref
Weaknesses CWE-1333
CWE-400
References
Metrics cvssV4_0

{'score': 2.7, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U'}


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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-01-10T04:46:12.423Z

Reserved: 2026-01-08T19:23:09.855Z

Link: CVE-2026-22691

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-01-10T05:16:08.680

Modified: 2026-01-10T05:16:08.680

Link: CVE-2026-22691

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

No data.

Weaknesses