# CVE-2026-84309

## Summary

- **CVE ID:** CVE-2026-84309
- **Severity:** MEDIUM
- **CVSS Score:** 6.9 (CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N)
- **CWE:** CWE-835
- **Published:** Sep 1, 2026
- **Last Modified:** Sep 2, 2026

## Description

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.

## Affected Products

- py-pdf — pypdf (< 6.16.0)

## References

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

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.13%
- **EPSS Percentile:** 2.7

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-11._