Spin is the developer tool for building and running serverless applications powered by WebAssembly. Prior to 2.4.3, some specifically configured Spin applications that use `self` requests without a specified URL authority can be induced to make requests to arbitrary hosts via the `Host` HTTP header. The following conditions need to be met for an application to be vulnerable: 1. The environment Spin is deployed in routes requests to the Spin runtime based on the request URL instead of the `Host` header, and leaves the `Host` header set to its original value; 2. The Spin application's component handling the incoming request is configured with an `allow_outbound_hosts` list containing `"self"`; and 3. In reaction to an incoming request, the component makes an outbound request whose URL doesn't include the hostname/port. Spin 2.4.3 has been released to fix this issue.

GitHub, Inc. AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

GitHub, Inc. CWE-610

GitHub, Inc. https://github.com/fermyon/spin/commit/b3db535c9edb72278d4db3a201f0ed214e561354 [No types assigned]

GitHub, Inc. https://github.com/fermyon/spin/security/advisories/GHSA-f3h7-gpjj-wcvh [No types assigned]