GHSA-w62v-xxxg-mg59

Suggest an improvement
Source
https://github.com/advisories/GHSA-w62v-xxxg-mg59
Import Source
https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/07/GHSA-w62v-xxxg-mg59/GHSA-w62v-xxxg-mg59.json
JSON Data
https://api.test.osv.dev/v1/vulns/GHSA-w62v-xxxg-mg59
Aliases
Downstream
CGA (73)
MINI (9)
Published
2026-07-21T18:33:50Z
Modified
2026-07-21T18:45:58Z
Severity
  • 6.1 (Medium) CVSS_V3 - CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N CVSS Calculator
Summary
Hono: Server-Side XSS via JSX Escaping Bypass in cx() Utility
Details

Summary

cx() in hono/css composes class names from plain strings but marks the result as already-escaped without HTML-escaping the input. When the result is used as a JSX class attribute during server-side rendering, the value is written into the attribute unescaped, so untrusted input can break out of the class attribute and inject arbitrary markup, leading to Cross-Site Scripting (XSS).

Details

Because the composed value is treated as pre-escaped, the HTML attribute escaping normally applied to interpolated values is skipped, and characters such as " pass through unescaped — allowing a value to terminate the attribute and add further attributes or elements. This arises when an application passes untrusted, user-controlled input as a class name to cx(), for example when merging a base class with an externally provided className.

Impact

During server-side rendering, an attacker who controls a value passed to cx() can inject arbitrary HTML into the page, resulting in stored or reflected XSS in the victim's browser.

This may lead to:

  • Execution of attacker-controlled script in the victim's browser session.
  • Session hijacking, credential theft, or actions performed on behalf of the victim.

Applications are affected only if they render JSX server-side and pass untrusted input as a class name to cx().

Database specific 
{
    "cwe_ids": [
        "CWE-116",
        "CWE-79"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-07-21T18:33:50Z",
    "nvd_published_at": "2026-07-08T17:17:27Z",
    "severity": "MODERATE"
}
References

Affected packages

npm / hono

Package

Name
hono
View open source insights on deps.dev
Purl
pkg:npm/hono

Affected ranges

Type
SEMVER
Events
Introduced
4.0.0
Fixed
4.12.27

Database specific

source 
"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/07/GHSA-w62v-xxxg-mg59/GHSA-w62v-xxxg-mg59.json"