CVE-2026-24688: pypdf has possible Infinite Loop when processing outlines/bookmarks

Severity: medium (CVSS 4.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-01-27 · updated 2026-06-17
Weakness: CWE-835

Description

pypdf is a free and open-source pure-python PDF library. An attacker who uses an infinite loop vulnerability that is present in versions prior to 6.6.2 can craft a PDF which leads to an infinite loop. This requires accessing the outlines/bookmarks. This has been fixed in pypdf 6.6.2. If projects cannot upgrade yet, consider applying the changes from PR #3610 manually.

Affected products

py-pdf pypdf: before 6.6.2 — fixed in 6.6.2

How to fix

Upgrade to a fixed version: py-pdf pypdf 6.6.2. Check the vendor advisory for mitigations.

References

https://github.com/py-pdf/pypdf/commit/b1282f8dcdc1a7b41ceab6740ffddfdf31b1fec1
https://github.com/py-pdf/pypdf/pull/3610
https://github.com/py-pdf/pypdf/releases/tag/6.6.2
https://github.com/py-pdf/pypdf/security/advisories/GHSA-2q4j-m29v-hq73

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