Vulnerability · Published Aug 23, 2026 · Assigned by VulnCheck

CVE-2026-8630justhtml before 1.12.0 Mutation XSS via Raw Text Elements

Medium 6.1

In plain English

A medium-severity cross-site scripting in justhtml from EmilStenstrom. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 18% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)6.1Medium

Exploit odds (30 days)0.3%top 81.8% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official description

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.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
PyPI	justhtml	1.12.0	GHSA-qvc2-mg72-jjhx

Affected products (as reported)

Vendor	Product	Versions
EmilStenstrom	justhtml	0 – before 1.12.0

Weakness: CWE-79 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

References

GitHub Security Advisory (GHSA-qvc2-mg72-jjhx) vendor-advisory
VulnCheck Advisory: justhtml before 1.12.0 Mutation XSS via Raw Text Elements third-party-advisory