# CVE-2026-56761: hono XSS — Fixed in 4.12.14

📦 npm

Not in CISA KEV

# CVE-2026-56761 — hono

CVE-2026-56761 is a Cross-site Scripting (XSS) vulnerability in hono. A fix is available for hono — see the affected versions and patch details below.

hono - HTML Injection via Improper JSX Attribute Name Handling in SSR

Also known as[GHSA-458j-xx4x-4375](/vulnerability/GHSA-458j-xx4x-4375)

Published

Jun 24, 2026

Updated

Oct 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 9, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

## Exploitation Status

### No confirmed exploitation observed yet

-   CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-56761.

## EPSS Exploitation Probability

[via FIRST.org ↗](https://www.first.org/epss/)

0.3%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs22th percentile — riskier than 22% of all scored CVEsHighest risk

0.00%0.26%0.53%0.79%0.2%0.3%Jul 26Oct 26Nov 26

Probability of exploitation in the next 30 days, from [FIRST.org EPSS](https://www.first.org/epss/).

## Real-World Exposure

1 pkg affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

7Kother npm packages depend on this — each one inherits the vulnerability until it's patched upstream

`hono`npm

104.3Mdownloads / week

## Description

### Summary

Improper handling of JSX attribute names in hono/jsx allows malformed attribute keys to corrupt the generated HTML output.

When untrusted input is used as attribute keys during server-side rendering, specially crafted keys can break out of attribute or tag boundaries and inject unintended HTML.

### Details

When rendering JSX elements to HTML strings, attribute values are escaped, but attribute names (keys) were previously inserted into the output without validation.

If an attribute name contains characters such as `"`, `>`, or whitespace, it can alter the structure of the generated HTML.

For example, malformed attribute names can:

-   Break out of the current attribute and introduce unintended additional attributes
-   Break out of the current HTML tag and inject new elements into the output

This issue arises when untrusted input (such as query parameters or form data) is used as JSX attribute keys during server-side rendering.

### Impact

An attacker who can control attribute keys used in JSX rendering may inject unintended attributes or HTML elements into the generated output.

This may lead to:

-   Injection of unexpected HTML attributes
-   Corruption of the HTML structure
-   Potential cross-site scripting (XSS) if combined with unsafe usage patterns

This issue affects applications that pass untrusted input as JSX attribute keys during server-side rendering.

## Affected Packages

1 total 1 fixed

Ecosystem

Package

Vulnerable range

Fix

📦npm

`hono` 

all versions

4.12.14`npm install hono@4.12.14`

## Affected Products

1 product · 1 configurations

Application

`hono`hono

< 4.12.14

range

## Detection & mitigation playbook

Open-source dependency

1.  ### Detect
    
    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for hono, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
    
2.  ### Fix
    
    Update hono to 4.12.14 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-56761 is resolved across your whole dependency graph.
    
3.  ### Workarounds
    
    Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.
    

## Frequently Asked Questions

\## Summary Improper handling of JSX attribute names in hono/jsx allows malformed attribute keys to corrupt the generated HTML output. When untrusted input is used as attribute keys during server-side rendering, specially crafted keys can break out of attribute or tag boundaries and inject unintended HTML. ## Details When rendering JSX elements to HTML strings, attribute values are escaped, but attribute names (keys) were previously inserted into the output without validation. If an attribute name contains characters such as \`"\`, \`>\`, or whitespace, it can alter the structure of the genera

O3 Security · Impact-Aware SCA

### Is CVE-2026-56761 in your dependencies?

Find it across npm, including transitive dependencies.

[Scan my dependencies](/book-demo) [How O3 SCA works](/impact-aware-sca)