CVE-2026-59937: pypdf: Possible long runtimes for repeated malformed cross-reference entries

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-07-08 · updated 2026-10-25
Weakness: CWE-400

Description

pypdf is a free and open-source pure-python PDF library. Prior to 6.14.0, an attacker can craft a PDF with repeated malformed cross-reference streams that cause pypdf to spend long runtimes recovering broken cross-reference table entries. This issue is fixed in version 6.14.0.

Affected products

py-pdf pypdf: before 6.14.0 — fixed in 6.14.0

How to fix

Upgrade to a fixed version: py-pdf pypdf 6.14.0. Check the vendor advisory for mitigations.

References

https://github.com/py-pdf/pypdf/commit/b5fc5aa714f4b696fb9b1deaa35a9e4a4eb50dae
https://github.com/py-pdf/pypdf/pull/3887
https://github.com/py-pdf/pypdf/releases/tag/6.14.0
https://github.com/py-pdf/pypdf/security/advisories/GHSA-55h5-xmcq-c37v

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