CVE-2026-126355: Hono: `csrf()` does not check requests sent by hyperlink auditing (`text/ping`)
Summary
csrf() validates a request only when its Content-Type is one of the three types an HTML form can send. Chromium's hyperlink auditing (<a ping>) sends a cross-origin POST with the user's cookies and the content type text/ping, which is not in that list. The middleware does not look at Origin or Sec-Fetch-Site for such a request, so it is passed to the handler.
Details
The middleware skips the origin check when the content type is not one that a form submission produces. The assumption was that any other content type requires a CORS preflight and therefore cannot be sent cross-origin with credentials. Hyperlink auditing is an exception: Chrome and Edge send the ping as a credentialed POST without a preflight, with a fixed body and Content-Type: text/ping.
A page on another origin can therefore trigger a POST to any URL of the application. The csrf() options for origin and secFetchSite do not change the outcome, because neither header is evaluated for the request.
The request body is fixed, so only actions whose effect does not depend on the body can be triggered. Firefox does not send pings by default. As with any CSRF, the user's cookie must be sent with the request, which with the default SameSite=Lax means a same-site origin or a cookie set with SameSite=None.
Impact
A user who visits a malicious page in Chrome or Edge while logged in to an application protected by csrf() can be made to send a state-changing request to that application, such as logging out, deleting a resource, or toggling a setting that is selected by the path or query string.
This issue affects applications that rely on csrf() as their CSRF protection and expose state-changing endpoints whose effect does not depend on the request body.
Workarounds
Reject requests with a Content-Type of text/ping in a middleware registered before csrf(), or set session cookies with SameSite=Strict.
Other sources
Hono is a Web application framework that provides support for any JavaScript runtime. Prior to 4.13.16, csrf() limits origin validation to the content types normally sent by HTML forms and therefore does not validate text/ping requests generated by Chromium hyperlink auditing. Chrome and Edge can send a cross-origin credentialed POST without a CORS preflight through an <a ping> action, and the middleware then skips both Origin and Sec-Fetch-Site checks. The fixed request body limits exploitation to state-changing endpoints whose effect is selected by the path or query string and does not depend on submitted body data. The user's cookie must accompany the request, which generally requires a same-site origin or a cookie configured with SameSite=None, and Firefox does not send hyperlink-auditing pings by default. This issue is fixed in version 4.13.16.
— MITRE
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
npm/honoto a version that resolves this vulnerability.Fixed in 4.13.16 - Upgrade
Upgrade
Honoto a version that resolves this vulnerability.Fixed in 4.13.16 - Configuration
Register middleware before csrf() that rejects requests with a Content-Type of text/ping.
csrf() middleware Content-Type = text/ping rejected - Configuration
Set session cookies with SameSite=Strict.
session cookies SameSite = Strict
Event History
Frequently Asked Questions
Which users and browsers are realistically exposed?
Exposure requires a victim to be logged in to the application with cookies and to visit an attacker-controlled page. Chrome and Edge can send the relevant credentialed hyperlink-auditing POST; Firefox does not send pings by default.
What kinds of application actions can be triggered?
An attacker can trigger a POST to any application URL, but the ping request has a fixed body. The practical impact is therefore limited to state-changing actions whose effect does not depend on attacker-controlled request-body data.
Do the csrf() origin and secFetchSite options mitigate this issue?
No. For text/ping requests, the middleware does not evaluate either Origin or Sec-Fetch-Site, so configuring those options does not change the outcome.
How can I determine whether an endpoint is at risk?
Identify POST endpoints protected by csrf() that accept an authenticated cookie-based request and perform a state-changing action without requiring meaningful request-body values. Such endpoints may be reachable through a cross-origin text/ping request from Chrome or Edge.