Ratpack is a toolkit for creating web applications. In versions prior to 1.9.0, a user supplied `X-Forwarded-Host` header can be used to perform cache poisoning of a cache fronting a Ratpack server if the cache key does not include the `X-Forwarded-Host` header as a cache key. Users are only vulnerable if they do not configure a custom `PublicAddress` instance. For versions prior to 1.9.0, by default, Ratpack utilizes an inferring version of `PublicAddress` which is vulnerable. This can be used to perform redirect cache poisoning where an attacker can force a cached redirect to redirect to their site instead of the intended redirect location. The vulnerability was patched in Ratpack 1.9.0. As a workaround, ensure that `ServerConfigBuilder::publicAddress` correctly configures the server in production.
Affected: Maven: io.ratpack:ratpack-core
A user supplied `X-Forwarded-Host` header can be used to perform cache poisoning of a cache fronting a Ratpack server if the cache key does not include the `X-Forwarded-Host` header as a cache key.
Users are only vulnerable if they do not configure a custom `PublicAddress` instance. A custom `PublicAddress` can be specified by using [ServerConfigBuilder::publicAddress](https://ratpack.io/manual/current/api/ratpack/server/ServerConfigBuilder.html#publicAddress-java.net.URI-). For versions prior to 1.9.0, by default, Ratpack utilizes an inferring version of `PublicAddress` which is vulnerable.
### Impact
This can be used to perform redirect cache poisoning where an attacker can force a cached redirect to redirect to their site instead of the intended redirect location.
### Patches
As of Ratpack 1.9.0, two changes have been made that mitigate this vulnerability:
1. The default PublicAddress implementation no longer infers the address from the request context, instead relying on the configured bind host/port 2. Relative redirects issued by the application are no longer absolutized; they are passed through as-is
### Workarounds
In production, ensure that [ServerConfigBuilder::publicAddress](https://ratpack.io/manual/current/api/ratpack/server/ServerConfigBuilder.html#publicAddress-java.net.URI-) correctly configures the server.
### References - https://portswigger.net/web-security/web-cache-poisoning