Cross-site scripting in hono - CVE-2026-59895
Published: July 24, 2026
Vulnerability identifier: #VU139275
CSH Severity: Medium
CVSS v4: 5.1 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N]
CVE-ID: CVE-2026-59895
CWE-ID: CWE-79
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to execute arbitrary script in the victim's browser.
The vulnerability exists due to improper neutralization of input during web page generation in the cx() utility in hono/css when rendering JSX class attributes during server-side rendering with untrusted input. A remote attacker can supply a crafted class name value to inject arbitrary markup and execute arbitrary script in the victim's browser.
Applications are affected only if they render JSX server-side and pass untrusted input as a class name to cx(). User interaction is required for a victim to load the rendered page.
Affected software
hono
How to mitigate CVE-2026-59895
Install security update from vendor's website.
hono - update to 4.12.27