CVE-2026-7808

Summary

justhtml before 1.16.0 contains multiple HTML sanitization bypass issues that can allow active/dangerous content (e.g., script or style) to survive sanitization, potentially leading to cross-site scripting. The issues primarily affect advanced usage rather than the default JustHTML(…, sanitize=True) path for ordinary parsed HTML: mutating or reusing sanitization policy objects (including exported defaults) could weaken later sanitization; programmatic DOM input to sanitize()/sanitize_dom() could miss mixed-case tag names (e.g., ScRiPt, StYlE); crafted programmatic doctype names could serialize into active markup; and custom policies preserving SVG or MathML could allow animation elements, presentation attributes with external url(…) references, or DOM trees mislabeled as namespace="html" to bypass foreign-content checks. Fixed in 1.16.0.

Affected Software

Weaknesses

• CWE-20: Improper Input Validation

References

• https://github.com/EmilStenstrom/justhtml/security/advisories/GHSA-4p64-v8f5-r2gx
• https://www.vulncheck.com/advisories/justhtml-before-multiple-security-issues-via-sanitization

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