CVE-2026-27024: pypdf has a possible infinite loop when processing TreeObject

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-02-20 · updated 2026-06-17
Weakness: CWE-835

Description

pypdf is a free and open-source pure-python PDF library. Prior to 6.7.1, an attacker who uses this vulnerability can craft a PDF which leads to an infinite loop. This requires accessing the children of a TreeObject, for example as part of outlines. This vulnerability is fixed in 6.7.1.

Affected products

py-pdf pypdf: before 6.7.1 — fixed in 6.7.1

How to fix

Upgrade to a fixed version: py-pdf pypdf 6.7.1. Check the vendor advisory for mitigations.

References

https://github.com/py-pdf/pypdf/commit/bd2f6d052fe5941e85e37082c2a43453d48d1295
https://github.com/py-pdf/pypdf/pull/3645
https://github.com/py-pdf/pypdf/releases/tag/6.7.1
https://github.com/py-pdf/pypdf/security/advisories/GHSA-996q-pr4m-cvgq

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