Resource exhaustion in Markdown-It
CVE-2026-111766
markdown-it is a Markdown parser. Prior to 14.3.3 and 15.0.3, when the html option or commonmark preset is enabled and the constructs occur inside a paragraph, attacker-controlled Markdown containing repeated unterminated inline HTML comments, processing instructions, declarations, or CDATA sections reaches src/rules_inline/html_inline.ts. Its HTML_TAG_RE match searches the remaining suffix for the appropriate terminator; when no terminator is present, parsing advances to the next opener and repeats the match over overlapping input, causing quadratic processing and denial of service through event-loop blocking or an unresponsive browser main thread. HTML blocks and the default HTML-disabled configuration are not affected by these payloads. This issue is fixed in versions 14.3.3 and 15.0.3.
Vulnerability class: DoS (Denial of Service)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 3.7 (Low). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
- Markdown-It — versions < 14.3.3, >= 15.0.0, < 15.0.3
Weakness classification (CWE)
References
- github.com/markdown-it/markdown-it/security/advisories/GHSA-vfgh-jcmw-g37q
- github.com/markdown-it/markdown-it/commit/928bc8c11ded60181c0e7fc5aa954eec582e8…
- github.com/markdown-it/markdown-it/commit/d99f48839d37af6fd8a2617516c43dab90755…
- github.com/markdown-it/markdown-it/releases/tag/14.3.3
- github.com/markdown-it/markdown-it/releases/tag/15.0.3
Frequently asked questions
- What is CVE-2026-111766?
- CVE-2026-111766 is a low-severity vulnerability in Markdown-It, classified under Uncontrolled Resource Consumption. CVSS score: 3.7/10. Published 2026-10-19.
- How severe is CVE-2026-111766?
- Low severity. CVSS v3 base score is 3.7 out of 10.