CVE-2026-86433 PUBLISHED

commonmark 1.5.0 before 2.8.4 Denial of Service via Attributes

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 Attributes extension where AttributesListener::findTargetAndDirection() performs quadratic-time sibling list scanning. Unauthenticated attackers can submit approximately 32 KB of repeated attribute blocks to cause parsing to take over 5 seconds, exhausting 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-2026-86433 PUBLISHED

commonmark 1.5.0 before 2.8.4 Denial of Service via Attributes

Metrics

Product Status

Credits

References

Problem Types