CVE-2026-56761

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.

How to fix CVE-2026-56761

To remediate CVE-2026-56761, upgrade the affected package to a fixed version below.

• —upgrade to 4.12.14 or later

Is CVE-2026-56761 being exploited?

Low — EPSS is 0.2%, meaning exploitation activity has not been observed at scale.

Affected packages (1)

• from 0, < 4.12.14

CVSS scores