Answer in brief
CVE-2026-5751 records a Medium severity (CVSS 6.1) vulnerability in justhtml before 1.14.0 Mutation XSS via custom sanitization policies. The current sources do not mark it as known exploited. The current feed maps EmilStenstrom/justhtml (generic), justhtml (pypi). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 6.1. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps EmilStenstrom/justhtml (generic), justhtml (pypi). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| EmilStenstrom/justhtmlgeneric | >=0 <1.14.0 | 1.14.0 |
| justhtmlpypi | >=1.13.0 <1.14.0 | 1.14.0 |
Published upstream
Aug 23, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Aug 26, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Aug 23, 2026
justhtml versions 1.13.0 and earlier contain a parser-differential / mutation cross-site scripting (mXSS) vulnerability when using a custom SanitizationPolicy that preserves foreign namespaces (e.g., drop_foreign_namespaces=False with allowlisted SVG/MathML elements or raw-text containers such as <style>). Specially crafted input can sanitize into markup that appears safe but becomes unsafe when re-parsed by a browser or another HTML parser, allowing markup injection. The default safe configuration (sanitize=True) is not affected. Fixed in 1.14.0.
Quoted source text, attributed separately from HOL analysis.