CVE-2026-86430

league/commonmark versions before 2.9.1 contain multiple denial of service vulnerabilities in fenced code block detection, reference link label lookup, and emphasis delimiter processing that perform super-linear work on crafted input. Attackers can submit specially crafted Markdown with long backtick runs, nested brackets, or delimiter sequences to consume disproportionate CPU time and prevent legitimate requests from completing.

CVSS v3 7.5 HIGH

7.5^/10

CVSS v3 : HIGH

Vector :

Exploitability : 3.9 / Impact : 3.6

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact NONE

Integrity Impact NONE

Availability Impact HIGH

Scope UNCHANGED

References

Link	Resource
https://github.com/thephpleague/commonmark/security/advisories/GHSA-j8pm-gj4c-rq4x	Mitigation Patch Vendor Advisory
https://www.vulncheck.com/advisories/league-commonmark-before-2.9.1-denial-of-service-via-parsing	Third Party Advisory

Configurations

Configuration 1 (hide)

cpe:2.3:a:thephpleague:commonmark:*:*:*:*:*:*:*:*

History

08 Oct 2026, 16:17

Type	Values Removed	Values Added
References	~~() https://github.com/thephpleague/commonmark/security/advisories/GHSA-j8pm-gj4c-rq4x - Mitigation, Vendor Advisory, Patch~~	() https://github.com/thephpleague/commonmark/security/advisories/GHSA-j8pm-gj4c-rq4x - Mitigation, Patch, Vendor Advisory

Information

Published : 2026-09-07 13:20

Updated : 2026-10-08 16:17

NVD link : CVE-2026-86430

Mitre link : CVE-2026-86430

CVE.ORG link : CVE-2026-86430

JSON object : View

Products Affected

thephpleague

commonmark

CWE

CWE-407

Inefficient Algorithmic Complexity

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