# hono/jsx unescaped string rendering in boundary components XSS

Source: https://junglewise.ai/threats/duplicate-advisory-hono-jsx-renders-plain-strings-unescaped-in-boundary-4e550189  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-19. Updated: 2026-10-01  
License: CC BY 4.0 with a link back

Severity: medium · CVSS 4.7 · Published 2026-09-19

hono is a JavaScript web framework that renders server-side templates to HTML. When hono/jsx renders untrusted strings in certain component boundaries (Suspense, ErrorBoundary, Context.Provider), it fails to escape HTML entities, allowing attackers to inject malicious scripts that execute in users' browsers. This could lead to session hijacking, credential theft, or defacement of web applications.

Technologies: [Hono](https://junglewise.ai/threats/technologies/hono-hono), [hono (npm)](https://junglewise.ai/threats/technologies/hono). Vendors: [Hono](https://junglewise.ai/threats/vendors/hono), [npm](https://junglewise.ai/threats/vendors/npm).

## Quick answers

**Is This vulnerability exploited in the wild?** No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.

**How severe is This vulnerability?** Medium severity, with a CVSS score of 4.7, published 19 September 2026.

**Which products and versions are affected?** Hono < 4.13.7; hono (npm) < 4.13.7.

**Is there a fix for This vulnerability?** A patch was published on 2026-09-04: Patched in version 4.13.7 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is This vulnerability attacked?** It is attacked over the network, in a software library.

**Am I affected?** Check whether you run Hono or hono (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability exists in hono/jsx's server-side rendering (renderToString/renderToReadableStream) where plain strings in Suspense fallbacks, ErrorBoundary children with async siblings, Context.Provider single children, and root values are treated as pre-escaped markup without HTML entity escaping. An attacker controlling such strings during server-side rendering can inject arbitrary HTML/JavaScript. The issue was patched in version 4.13.7; affected versions before that are vulnerable.

## Affected products

- hono hono < 4.13.7

## Timeline

- 2026-09-04: disclosed
- 2026-09-04: patched: Patched in version 4.13.7

## References

- [https://github.com/honojs/hono/security/advisories/GHSA-hxh3-vqpv-xpqv](https://github.com/honojs/hono/security/advisories/GHSA-hxh3-vqpv-xpqv)

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