CVE-2026-86432

commonmark versions from 2.0.0 before 2.8.4 contain a denial of service vulnerability in XmlRenderer that emits depth-proportional indentation for every XML tag. Attackers can provide deeply nested Markdown or AST structures to cause quadratic memory consumption and output amplification, exhausting server resources.

CVSS 4.0

6.9CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

CVSS 3.1

5.3CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

EPSS

0.4% chance of exploitation in the next 30 days; higher than 35% of CVEs (scores of 2026-10-25)

CWE

CWE-405

Published

2026-09-07

Modified

2026-10-08

Record from

the NVD, synced 2026-10-19

References

• https://github.com/thephpleague/commonmark/security/advisories/GHSA-mj63-m3rc-8ppr
• https://www.vulncheck.com/advisories/commonmark-2.0.0-before-2.8.4-denial-of-service-via-xml

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