CVE-2026-86435 PUBLISHED

commonmark 1.5.0 before 2.8.4 Denial of Service via Footnote

Assigner: VulnCheck
Reserved: 07.09.2026 Published: 07.09.2026 Updated: 07.09.2026

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.

CVSS 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
CVSS Score: 8.7

Exploitability Metrics		Vulnerable System Impact Metrics		Subsequent System Impact Metrics
Attack Vector	Network	Confidentiality	None	Confidentiality	None
Attack Complexity	Low	Integrity	None	Integrity	None
Attack Requirements	None	Availability	High	Availability	None
Privileges Required	None
User Interaction	None

CVSS 4.0

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS Score: 7.5

Attack Vector	Network	Scope	Unchanged
Attack Complexity	Low	Confidentiality Impact	None
Privileges Required	None	Integrity Impact	None
User Interaction	None	Availability Impact	High

CVSS 3.1

Product Status

Vendor	thephpleague
Product	commonmark
Versions	Default: unaffected affected from 1.5.0 to 2.8.4 (excl.) Version 2.8.4 is unaffected

CVE-2026-86435 PUBLISHED

commonmark 1.5.0 before 2.8.4 Denial of Service via Footnote

Metrics

Product Status

Credits

References

Problem Types