# CVE-2026-86433

## Summary

- **CVE ID:** CVE-2026-86433
- **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 2.8.4 contain a denial of service vulnerability in the Attributes extension where AttributesListener::findTargetAndDirection() performs quadratic-time sibling list scanning. Unauthenticated attackers can submit approximately 32 KB of repeated attribute blocks to cause parsing to take over 5 seconds, exhausting server resources.

## Affected Products

- thephpleague — commonmark (1.5.0)
- thephpleague — commonmark (2.8.4)

## References

- [CNA](https://github.com/thephpleague/commonmark/security/advisories/GHSA-g2gp-3wwq-f4ph)
- [CNA](https://www.vulncheck.com/advisories/commonmark-1.5.0-before-2.8.4-denial-of-service-via-attributes)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.29%
- **EPSS Percentile:** 21.5

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-10._