CVE-2026-59895

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

Published Jul 8, 2026 CVSS 3.1 · 6.1 Medium EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-w62v-xxxg-mg59 Hono: Server-Side XSS via JSX Escaping Bypass in cx() Utility
History
Type Values Removed Values Added
First Time appeared Hono
Hono hono
Vendors & Products Hono
Hono hono
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
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.
Title Hono: Server-Side XSS via JSX Escaping Bypass in cx() Utility
Weaknesses CWE-116
CWE-79
References
Metrics cvssV3_1

{'score': 6.1, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Jul 8, 2026, 7:41 PM
Reserved
Jul 7, 2026, 4:40 PM
Status
Analyzed
Published
Jul 8, 2026, 5:17 PM
Modified
Oct 25, 2026, 5:10 PM