Vulnerability in Thephpleague Commonmark
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L.
EPSS exploit prediction
EPSS: 0.004 (35.0th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 35th percentile — 35.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.004 · change: +0.002
Affected products
Weakness classification (CWE)
References
- github.com/thephpleague/commonmark/security/advisories/GHSA-mj63-m3rc-8ppr (vendor-advisory)
- www.vulncheck.com/advisories/commonmark-2.0.0-before-2.8.4-denial-of-service-vi… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-86432?
- CVE-2026-86432 is a medium-severity vulnerability in Thephpleague Commonmark, classified under Asymmetric Resource Consumption (Amplification). CVSS score: 5.3/10. Published 2026-09-07.
- How severe is CVE-2026-86432?
- Medium severity. CVSS v3 base score is 5.3 out of 10.