CVE-2021-39199
10.0 · CRITICALOverview
CVE-2021-39199 is a critical-severity vulnerability affecting remark remark-html. It was published on September 7, 2021 and has a CVSS 3.1 base score of 10.0 (CRITICAL).
This vulnerability has a CVSS 3.1 base score of 10.0, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
Technical Description
remark-html is an open source nodejs library which compiles Markdown to HTML. In affected versions the documentation of remark-html has mentioned that it was safe by default. In practice the default was never safe and had to be opted into. That is, user input was not sanitized. This means arbitrary HTML can be passed through leading to potential XSS attacks. The problem has been patched in 13.0.2 and 14.0.1: `remark-html` is now safe by default, and the implementation matches the documentation. On older affected versions, pass `sanitize: true` if you cannot update.
Remediation
Check the references section for vendor advisories and patches from remark. Update remark-html to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
Affected Products
| Vendor | Product | Versions | Status |
|---|---|---|---|
| remark | remark-html | >= 0, < 13.0.2 | Affected |
References
Frequently Asked Questions
What is CVE-2021-39199?
CVE-2021-39199 is a critical-severity vulnerability affecting remark remark-html. It was published on September 7, 2021 and has a CVSS 3.1 base score of 10.0 (CRITICAL).
How severe is CVE-2021-39199?
This vulnerability has a CVSS 3.1 base score of 10.0, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
How do I fix or remediate CVE-2021-39199?
Check the references section for vendor advisories and patches from remark. Update remark-html to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
How can CyberStrike help with CVE-2021-39199?
CyberStrike's AI-powered security agents can automatically detect CVE-2021-39199 across your infrastructure using autonomous pentesting, DAST scanning, and HackBrowser. The platform continuously monitors for known vulnerabilities and provides actionable remediation guidance prioritized by real-world exploitability.
How CyberStrike Helps
AI agents map your attack surface to find vulnerabilities like this one.
Automated penetration testing that runs continuously, not just quarterly.
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Browser-based exploitation validates findings with real proof-of-concept.
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