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GHSA-458j-xx4x-4375

MediumCVSS 4.3 / 10
Published Apr 16, 2026·Last modified Apr 16, 2026
Affected Components(0)

No affected components available

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.

Risk Scores
Base Score
4.3

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. The attacker needs the user to perform some action, like clicking a link. The impact is confined to the system where the vulnerability exists. There is a low impact on the integrity of the data.

Threat Intelligence
4.0

Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.

EPSS
0.17%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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Medium severity
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