commonmark versions from 1.5.0 before 2.8.4 contain a denial of service vulnerability in the Footnote extension that fails to deduplicate footnote definitions. Attackers can craft documents with duplicate footnote definitions and references to create quadratic output expansion, consuming excessive memory and CPU to exhaust server resources.

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Fixes

Solution

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Workaround

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History

Mon, 07 Sep 2026 13:00:00 +0000

Type Values Removed Values Added
Description commonmark versions from 1.5.0 before 2.8.4 contain a denial of service vulnerability in the Footnote extension that fails to deduplicate footnote definitions. Attackers can craft documents with duplicate footnote definitions and references to create quadratic output expansion, consuming excessive memory and CPU to exhaust server resources.
Title commonmark 1.5.0 before 2.8.4 Denial of Service via Footnote
First Time appeared Thephpleague
Thephpleague commonmark
Weaknesses CWE-407
CPEs cpe:2.3:a:thephpleague:commonmark:*:*:*:*:*:*:*:*
Vendors & Products Thephpleague
Thephpleague commonmark
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}

cvssV4_0

{'score': 8.7, 'vector': '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'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: VulnCheck

Published:

Updated: 2026-09-07T12:53:53.897Z

Reserved: 2026-09-07T12:34:31.457Z

Link: CVE-2026-86435

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-09-07T13:20:43.013

Modified: 2026-09-07T13:20:43.013

Link: CVE-2026-86435

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-09-07T16:00:13Z

Weaknesses