CVE-2026-86429 (GCVE-0-2026-86429)

Vulnerability from cvelistv5 – Published: 2026-09-07 12:53 – Updated: 2026-10-08 15:25
VLAI
Title
commonmark before 2.9.1 Denial of Service via SmartPunct and Attributes
Summary
The league/commonmark (thephpleague/commonmark) library in versions >= 1.5.0 and < 2.9.1 contains quadratic parsing complexity in its SmartPunctExtension and AttributesExtension. When either extension is explicitly registered on the Environment (they are not enabled by default and are excluded from the standard CommonMark and GitHub-Flavored Markdown converters), an unauthenticated attacker can submit small, specially crafted Markdown documents — such as text alternating with unpaired quotes, contiguous runs of block-level attribute blocks, or repeated class attributes — to trigger disproportionate CPU consumption and cause a denial of service. Fixed in 2.9.1.
Severity
8.7 (High)
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
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
SSVC
Exploitation: none Automatable: yes Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-09-18 17:41 UTC
CWE
  • CWE-407 - Inefficient Algorithmic Complexity
Assigner
VulnCheck CNA under the mitre root
CNA scorecard B 84/100 over 7011 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
thephpleague commonmark Affected: 1.5.0 , < 2.9.1 (semver)
Unaffected: 2.9.1 (semver)
    cpe:2.3:a:thephpleague:commonmark:*:*:*:*:*:*:*:*
Create a notification for this product.
Date Public
2026-08-09 00:00
Credits
colinodell
Show details on NVD website
To clipboard 

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