CVE-2026-24771

A Cross-Site Scripting (XSS) vulnerability exists in the ErrorBoundary component of the hono/jsx library. Under certain usage patterns, untrusted user-controlled strings may be rendered as raw HTML, allowing arbitrary script execution in the victim's browser.

Details

The issue is in the ErrorBoundary component (src/jsx/components.ts). ErrorBoundary previously forced certain rendered output paths to be treated as raw HTML, bypassing the library's default escaping behavior. This could result in unescaped rendering when developers pass user-controlled strings directly as children, or when fallbackRender returns user-controlled strings (for example, reflecting error messages that contain attacker input).

This vulnerability is only exploitable when an application renders untrusted user input within ErrorBoundary without appropriate escaping or sanitization.

Affected Components

• hono/jsx: ErrorBoundary component

Successful exploitation may allow attackers to execute arbitrary JavaScript in the victim’s browser (reflected XSS). Depending on the application context, this can lead to actions such as session compromise, data exfiltration, or performing unauthorized actions as the victim.

Untrusted input is rendered as active markup in a victim's browser, which can run script in their session. Typical impact: session or credential theft, and actions taken as the user.

CVE-2026-24771 has a CVSS score of 4.7 (Medium). The vector is network-reachable, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (4.11.7); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2026-24771? CVE-2026-24771 is a medium-severity cross-site scripting (XSS) vulnerability in hono (npm), affecting versions < 4.11.7. It is fixed in 4.11.7. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
2. How severe is CVE-2026-24771? CVE-2026-24771 has a CVSS score of 4.7 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of hono are affected by CVE-2026-24771? hono (npm) versions < 4.11.7 is affected.
4. Is there a fix for CVE-2026-24771? Yes. CVE-2026-24771 is fixed in 4.11.7. Upgrade to this version or later.
5. Is CVE-2026-24771 exploitable, and should I be worried? Whether CVE-2026-24771 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-24771 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-24771? Upgrade hono to 4.11.7 or later.