CVE-2026-111766

markdown-it: Quadratic-time denial of service in inline HTML parsing with html enabled

This is an availability issue affecting applications that render attacker-controlled Markdown with html: true, including applications using the commonmark preset.

On Node.js, a synchronous render() call can occupy a CPU core and block the event loop for seconds or tens of seconds, delaying other requests handled by the same process. Repeated submissions can cause denial of service. Browser applications can similarly become unresponsive when rendering on the main thread.

Sanitizing the generated HTML afterwards does not prevent the issue because the expensive processing occurs during Markdown rendering.

The default configuration, with HTML disabled, is unaffected by these payloads. Disabling HTML or limiting input size can reduce exposure while a fix is prepared.

The reported affected release is 15.0.2; the full affected version range has not been established.

Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service. Typical impact: denial of service.

CVE-2026-111766 has a CVSS score of 3.7 (Low). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (14.3.3, 15.0.3); upgrading removes the vulnerable code path.

Kodem intelligence

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1. What is CVE-2026-111766? CVE-2026-111766 is a low-severity uncontrolled resource consumption vulnerability in markdown-it (npm), affecting versions < 14.3.3. It is fixed in 14.3.3, 15.0.3. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.
2. How severe is CVE-2026-111766? CVE-2026-111766 has a CVSS score of 3.7 (Low). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of markdown-it are affected by CVE-2026-111766? markdown-it (npm) versions < 14.3.3 is affected.
4. Is there a fix for CVE-2026-111766? Yes. CVE-2026-111766 is fixed in 14.3.3, 15.0.3. Upgrade to this version or later.
5. Is CVE-2026-111766 exploitable, and should I be worried? Whether CVE-2026-111766 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-111766 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-111766?
   • Upgrade markdown-it to 14.3.3 or later
   • Upgrade markdown-it to 15.0.3 or later

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