CVE-2026-59895: CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') in honojs hono
A cross-site scripting (XSS) vulnerability exists in honojs hono versions from 4.0.0 up to but not including 4.12.27. The cx() function in hono/css composes class names from plain strings but marks them as already escaped without properly HTML-escaping input. This allows untrusted className values used in JSX class attributes during server-side rendering to inject arbitrary markup. The issue is fixed in version 4.12.27.
AI Analysis
Technical Summary
CVE-2026-59895 is a cross-site scripting vulnerability in the hono JavaScript web framework affecting versions >=4.0.0 and <4.12.27. The vulnerability arises because the cx() function in hono/css treats composed class names as already escaped without performing HTML escaping on input strings. This improper neutralization of input during web page generation allows attackers to inject arbitrary markup by breaking out of JSX class attributes during server-side rendering. The vulnerability is addressed in version 4.12.27.
Potential Impact
An attacker can exploit this vulnerability to inject arbitrary HTML or script code into web pages rendered by affected versions of hono, potentially leading to client-side code execution, data theft, or session hijacking. The CVSS score of 6.1 reflects a medium severity with network attack vector, low attack complexity, no privileges required, user interaction required, and partial confidentiality and integrity impact.
Mitigation Recommendations
Upgrade to hono version 4.12.27 or later, where this vulnerability is fixed. No other official remediation or temporary fixes are documented. Patch status is confirmed by the vendor advisory stating the issue is fixed in 4.12.27.
CVE-2026-59895: CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') in honojs hono
Description
A cross-site scripting (XSS) vulnerability exists in honojs hono versions from 4.0.0 up to but not including 4.12.27. The cx() function in hono/css composes class names from plain strings but marks them as already escaped without properly HTML-escaping input. This allows untrusted className values used in JSX class attributes during server-side rendering to inject arbitrary markup. The issue is fixed in version 4.12.27.
CVSS v3.1
Score 6.1medium
Affected software
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AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-59895 is a cross-site scripting vulnerability in the hono JavaScript web framework affecting versions >=4.0.0 and <4.12.27. The vulnerability arises because the cx() function in hono/css treats composed class names as already escaped without performing HTML escaping on input strings. This improper neutralization of input during web page generation allows attackers to inject arbitrary markup by breaking out of JSX class attributes during server-side rendering. The vulnerability is addressed in version 4.12.27.
Potential Impact
An attacker can exploit this vulnerability to inject arbitrary HTML or script code into web pages rendered by affected versions of hono, potentially leading to client-side code execution, data theft, or session hijacking. The CVSS score of 6.1 reflects a medium severity with network attack vector, low attack complexity, no privileges required, user interaction required, and partial confidentiality and integrity impact.
Mitigation Recommendations
Upgrade to hono version 4.12.27 or later, where this vulnerability is fixed. No other official remediation or temporary fixes are documented. Patch status is confirmed by the vendor advisory stating the issue is fixed in 4.12.27.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-07-07T16:40:07.983Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a4e7ad4c9d9e3dbe36a7d72
Added to database: 07/08/2026, 16:29:08 UTC
Last enriched: 07/22/2026, 00:58:12 UTC
Last updated: 08/22/2026, 22:52:15 UTC
Views: 78
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