Hono: Cookie Attribute Injection via Unsanitized domain and path in setCookie()

Hono is a Web application framework that provides support for any JavaScript runtime. Prior to version 4.12.4, the setCookie() utility did not validate semicolons (;), carriage returns (\r), or newline characters (\n) in the domain and path options when constructing the Set-Cookie header. Because cookie attributes are delimited by semicolons, this could allow injection of additional cookie attributes if untrusted input was passed into these fields. This issue has been patched in version 4.12.4.

Hono is a Web application framework that provides support for any JavaScript runtime. Prior to version 4.12.4, the setCookie() utility did not validate semicolons (;), carriage returns (\r), or newline characters (\n) in the domain and path options when constructing the Set-Cookie header. Because cookie attributes are delimited by semicolons, this could allow injection of additional cookie attributes if untrusted input was passed into these fields. This issue has been patched in version 4.12.4.

Hono is a Web application framework that provides support for any JavaScript runtime. Prior to version 4.12.4, the setCookie() utility did not validate semicolons (;), carriage returns (\r), or newline characters (\n) in the domain and path options when constructing the Set-Cookie header. Because cookie attributes are delimited by semicolons, this could allow injection of additional cookie attributes if untrusted input was passed into these fields. This issue has been patched in version 4.12.4.

## Summary The `setCookie()` utility did not validate semicolons (`;`), carriage returns (`\r`), or newline characters (`\n`) in the `domain` and `path` options when constructing the `Set-Cookie` header. Because cookie attributes are delimited by semicolons, this could allow injection of additional cookie attributes if untrusted input was passed into these fields. ## Details `setCookie()` builds the `Set-Cookie` header by concatenating option values. While the cookie value itself is URL-encoded, the `domain` and `path` options were previously interpolated without rejecting unsafe characters. Including `;`, `\r`, or `\n` in these fields could result in unintended additional attributes (such as `SameSite`, `Secure`, `Domain`, or `Path`) being appended to the cookie header. Modern runtimes prevent full header injection via CRLF, so this issue is limited to attribute-level manipulation within a single `Set-Cookie` header. The issue has been fixed by rejecting these characters in the `domain` and `path` options. ## Impact An attacker may be able to manipulate cookie attributes if an application passes user-controlled input directly into the `domain` or `path` options of `setCookie()`. This could affect cookie scoping or security attributes depending on browser behavior. Exploitation requires application-level misuse of cookie options.