High severity · published Sep 7, 2026
CVE-2026-86428
commonmark 1.5.0 before 2.10.0 Denial of Service via Attributes
7.5
CVSS
0.5%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.5% · higher than 42% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
CO
commonmark · thephpleague
1.5.0 before 2.10.0 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-86428
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-86428
vendor-advisory
https://github.com/thephpleague/commonmark/security/advisories/GHSA-8rr7-cvq3-gmfh
third-party-advisory
https://www.vulncheck.com/advisories/commonmark-1.5.0-before-2.10.0-denial-of-service-via-attributes
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