CVE-2026-92106: lazy_html serializes SVG and MathML style and script text unescaped, allowing mutation XSS

Severity: low (CVSS 2.3 v4.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-09-25 · updated 2026-09-25
Weakness: CWE-79

Description

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in dashbitco lazy_html allows mutation XSS via a parse and serialize round-trip of attacker-supplied HTML. LazyHTML.to_html/2 and LazyHTML.Tree.to_html/2 decide whether to escape an element's text from its tag name alone. A style or script element inside SVG or MathML foreign content is parsed with character references decoded, but is serialized as an HTML raw-text element, so its text is emitted unescaped. Encoded markup such as </style><img src=x onerror=...> inside <svg><style> therefore closes the element on re-parse and becomes live markup. Applications that parse untrusted HTML with lazy_html, filter the document or tree, and serialize it for display are affected, since the payload is a plain text node that no element or attribute filter sees. This issue affects lazy_html: from 0.1.0 before 0.1.13.

Affected products

dashbitco lazy_html: from 0.1.0 before 0.1.13 — fixed in 0.1.13

How to fix

Upgrade to a fixed version: dashbitco lazy_html 0.1.13. Check the vendor advisory for mitigations.

References

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