Honojs Hono up to 4.13.15 Css Helper hono/css css helper cross site scripting

Summaryinfo

A vulnerability was found in Honojs Hono up to 4.13.15. It has been classified as problematic. Affected is the function css helper of the file hono/css of the component Css Helper. This manipulation causes cross site scripting. This vulnerability is tracked as CVE-2026-126359. The attack is possible to be carried out remotely. No exploit exists. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability has been found in Honojs Hono up to 4.13.15 and classified as problematic. Affected by this vulnerability is the function css helper of the file hono/css of the component Css Helper. The manipulation with an unknown input leads to a cross site scripting vulnerability. The CWE definition for the vulnerability is CWE-79. The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. As an impact it is known to affect integrity. The summary by CVE is:

Hono is a Web application framework that provides support for any JavaScript runtime. From 3.12.0 until 4.13.16, the css helper in hono/css escapes interpolated string values separately and therefore fails to neutralize a closing style tag when < ends the template text or a preceding value and / begins the next attacker-controlled value. During server-side rendering, the combined output can close the <Style /> element early and cause the remainder of the interpolated value to be interpreted as HTML. Applications that place an untrusted string immediately after < in a css template, including adjacent untrusted interpolations, can expose viewers to attacker-controlled HTML or script and information accessible to that page. Other uses of the css helper are not affected. This issue is fixed in version 4.13.16.

It is possible to read the advisory at github.com. This vulnerability is known as CVE-2026-126359 since 11/10/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. It demands that the victim is doing some kind of user interaction. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1059.007 according to MITRE ATT&CK.

Upgrading to version 4.13.16 eliminates this vulnerability.

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Productinfo

Vendor

• Honojs

Name

• Hono

Version

• 4.13.0
• 4.13.1
• 4.13.2
• 4.13.3
• 4.13.4
• 4.13.5
• 4.13.6
• 4.13.7
• 4.13.8
• 4.13.9
• 4.13.10
• 4.13.11
• 4.13.12
• 4.13.13
• 4.13.14
• 4.13.15

Website

• Product: https://github.com/honojs/hono/

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