CVE-2026-84309

pypdf is a free and open-source pure-python PDF library. Prior to 6.16.0, an attacker can craft a PDF whose cyclic tree structure causes pypdf/generic/_data_structures.py TreeObject.insert_child to follow /Next links indefinitely when a writing code path inserts a child, producing an infinite loop. This issue is fixed in version 6.16.0.

CVSS 4.0

6.9CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

CVSS 3.1

5.5CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

EPSS

0.2% chance of exploitation in the next 30 days; higher than 8% of CVEs (scores of 2026-10-25)

CWE

CWE-835

Published

2026-09-01

Modified

2026-10-05

Record from

the NVD, synced 2026-10-19

Affected

• pypdf_project:pypdf

Packages (OSV)

References

• https://github.com/py-pdf/pypdf/commit/c9ba557d565d57c53a0b3a0be06c0a4c29b0559b
• https://github.com/py-pdf/pypdf/pull/3964
• https://github.com/py-pdf/pypdf/releases/tag/6.16.0
• https://github.com/py-pdf/pypdf/security/advisories/GHSA-jp53-mhqp-8xcg

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