# CVE-2026-86428

## Summary

- **CVE ID:** CVE-2026-86428
- **Severity:** HIGH
- **CVSS Score:** 8.7 (CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N)
- **CWE:** CWE-407
- **Published:** Sep 7, 2026
- **Last Modified:** Sep 8, 2026

## Description

commonmark versions from 1.5.0 before 2.10.0 contain a denial of service vulnerability in the AttributesExtension when processing distinctly-named attributes. Attackers can submit Markdown with numerous distinct attribute names to cause quadratic-time attribute merging and filtering, consuming disproportionate CPU resources and preventing legitimate requests from completing.

## Affected Products

- thephpleague — commonmark (1.5.0)
- thephpleague — commonmark (2.10.0)

## References

- [CNA](https://github.com/thephpleague/commonmark/security/advisories/GHSA-8rr7-cvq3-gmfh)
- [CNA](https://www.vulncheck.com/advisories/commonmark-1.5.0-before-2.10.0-denial-of-service-via-attributes)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.28%
- **EPSS Percentile:** 20.2

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