CVE-2021-29479

Name of the Vulnerable Software and Affected Versions: Ratpack versions prior to 1.9.0

Description: The issue allows a user-supplied X-Forwarded-Host header 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. 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.

Recommendations: For versions prior to 1.9.0, ensure that ServerConfigBuilder::publicAddress correctly configures the server in production to mitigate the issue. As a temporary workaround, consider configuring a custom PublicAddress instance to prevent the use of the inferring version of PublicAddress. Update to Ratpack 1.9.0 or later, which includes changes that mitigate this vulnerability, such as a new default PublicAddress implementation and changes to relative redirects.