XSS in Emilstenstrom Justhtml
CVE-2026-8630
justhtml before 1.12.0 (versions <= 1.11.0) contains a mutation cross-site scripting (mXSS) vulnerability in the serialization of raw-text elements such as <style> and <script>. When a DOM tree is processed by sanitize_dom() using a custom policy that keeps these elements, text nodes inside them are serialized literally without escaping, allowing attacker-controlled text containing the matching closing tag sequence to break out of the raw-text context and inject arbitrary HTML into the serialized output. The default sanitization policy is not affected because it drops the contents of style and script.
Vulnerability class: XSS (Cross-Site Scripting)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.
EPSS exploit prediction
EPSS: 0.003 (16.6th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 17th percentile — 16.6% 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: 0.003 · change: +0.001
Affected products
Weakness classification (CWE)
References
- github.com/EmilStenstrom/justhtml/security/advisories/GHSA-qvc2-mg72-jjhx (vendor-advisory)
- www.vulncheck.com/advisories/justhtml-before-mutation-xss-via-raw-text-elements (third-party-advisory)
Frequently asked questions
- What is CVE-2026-8630?
- CVE-2026-8630 is a medium-severity vulnerability in Emilstenstrom Justhtml, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2026-08-23.
- How severe is CVE-2026-8630?
- Medium severity. CVSS v3 base score is 6.1 out of 10.