---
id: CVE-2026-86428
title: >-
  commonmark versions from 1.5.0 before 2.10.0 contain a denial of service
  vulnerability in the AttributesExtension when processing distinctly-named
  attributes
summary: >-
  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 …
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-407
vendor: thephpleague
product: commonmark
affected:
  - 'commonmark >= 1.5.0, < 2.10.0'
patched:
  - commonmark 2.10.0
published: '2026-09-07'
updated: '2026-09-09'
sourceUpdated: '2026-09-09T16:31:45.987'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-86428'
references:
  - url: >-
      https://github.com/thephpleague/commonmark/security/advisories/GHSA-8rr7-cvq3-gmfh
    label: disclosure@vulncheck.com
  - url: >-
      https://www.vulncheck.com/advisories/commonmark-1.5.0-before-2.10.0-denial-of-service-via-attributes
    label: disclosure@vulncheck.com
tags:
  - nvd
  - cve.org
epss: 0.00493
epssPercentile: 0.39786
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-09-08T12:50:42.697699Z'
ingestedAt: '2026-09-08T15:33:26.977Z'
---

## Overview

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

- `commonmark >= 1.5.0, < 2.10.0`

## Remediation

Upgrade past the affected range:

- `commonmark 2.10.0`