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.
Affected products
py-pdf: pypdf
References4
- github.com/py-pdf/pypdf/security/advisories/GHSA-4f6g-68pf-7vhv MitigationVendor Advisory
- github.com/py-pdf/pypdf/commit/294165726b646bb7799be1cc787f593f… Patch
- github.com/py-pdf/pypdf/pull/3594 Issue TrackingPatch
- github.com/py-pdf/pypdf/releases/tag/6.6.0 Release Notes
Metrics
- CVSS 3.1
-
5.3
MEDIUM
Score source: NVD
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L - CVSS 4.0
-
2.7
LOW
Score source: CNA
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/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - EPSS — exploit probability
- 0% percentile: 38 · as of 11 November 2026
- CWE
- CWE-400CWE-1333
Could this be exploited in your environment?
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