CVE-2026-59895

Hono: Server-Side XSS via JSX Escaping Bypass in cx() Utility

State: Published
Severity: 6.1 Medium
Published: Jul 8, 2026
Updated: Jul 8, 2026
Reserved: Jul 7, 2026

Description

Hono is a Web application framework that provides support for any JavaScript runtime. From 4.0.0 before 4.12.27, cx() in hono/css composes class names from plain strings but marks the result as already escaped without HTML-escaping the input, allowing untrusted className values used in a JSX class attribute during server-side rendering to break out of the attribute and inject arbitrary markup. This issue is fixed in version 4.12.27.

Scores

CVSS	Score	Vector	Source
3.1	6.1 Medium	CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N	GitHub_M

Weaknesses

CWE-79 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CWE-116 Improper Encoding or Escaping of Output

Affected Products

Product	Versions
honohonojs	>= 4.0.0, < 4.12.27Affected

References

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