CVE-2026-93981: hono/jsx before 4.13.7 Cross-Site Scripting via Unescaped Strings
Summary
hono/jsx does not HTML-escape a plain string placed directly as a child or fallback of Suspense or ErrorBoundary, as the only child of a Context.Provider, or as the root value of renderToString() / renderToReadableStream() from hono/jsx/dom/server. Such a string is emitted as markup instead of text.
Details
These paths stringify their input and treat the result as already-escaped HTML, so a plain string passes through unchanged. Notable cases:
- Suspense: a string child, or a string fallback while a child suspends. With streaming, the fallback reaches the browser in the initial chunk. - ErrorBoundary: a string child alongside an asynchronous sibling. The all-synchronous case was fixed in 4.11.7 (GHSA-9r54-q6cx-xmh5). - Context.Provider: a single string child. Multiple children are escaped. - hono/jsx/dom/server: a string, or an array containing strings, passed as the root.
A lone {children} forwarded by a wrapper component is enough to reach these paths. Strings wrapped in an element, values from raw() or the html helper, and client-side rendering with hono/jsx/dom are not affected.
Impact
An attacker who controls a string rendered in an affected position can inject arbitrary HTML into the server-rendered page, leading to cross-site scripting under the application's origin.
This issue affects applications that render untrusted strings directly in one of the positions above during server-side rendering.
Other sources
hono before 4.13.7 fails to HTML-escape plain strings rendered by hono/jsx as a child or fallback of Suspense, as a string child of ErrorBoundary alongside an asynchronous sibling, as the single child of a Context.Provider, or as the root value passed to renderToString() or renderToReadableStream() from hono/jsx/dom/server. These paths stringify their input and treat the result as already-escaped markup, so an attacker who controls such a string during server-side rendering can inject arbitrary HTML and execute script under the application's origin.
— NVD
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
npm/honoto a version that resolves this vulnerability.Fixed in 4.13.7 - Upgrade
Upgrade
honoto a version that resolves this vulnerability.Fixed in 4.13.7
Event History
Frequently Asked Questions
Which rendering patterns are affected?
The issue affects plain strings rendered as a child or Suspense fallback, as a string child of an ErrorBoundary with an asynchronous sibling, as the sole child of a Context.Provider, or as the root value supplied to renderToString() or renderToReadableStream() from hono/jsx/dom/server.
What must an attacker control to exploit this?
An attacker must be able to control a string that reaches one of the affected server-side rendering paths. The string is then treated as already-escaped markup, allowing injected HTML and script execution under the application's origin.
Are applications using other JSX rendering patterns affected?
The provided information identifies only the listed string-rendering paths. It does not state that all hono/jsx rendering of strings is affected.