The security of both a TUF client and repository implementations depend on the concept of trusted Metadata objects verifying the signatures over other Metadata that it delegates to. This verification process uses Targets.get_delegated_role(delegated_role: str) to find the delegation information. tuf.api.metadata.Targets.get_delegated_role() should ensure that the given delegated_rolename is actually a name of a role that is delegated by that Targets, but in the case of "succinct delegation" this does not happen. tuf.ngclient users are not impacted but direct users of tuf.api.metadata could be impacted. Impact If an attacker can make a Metadata API user run Targets.get_delegated_role() so that 1. the Targets uses succinct delegation 1. the delegated_role argument is not actually delegated by the Targets the result will be incorrect. This also means that if an attacker can make a Metadata API user run Targets.verify_delegate() or Targets.get_verification_result() so that 1. the delegating Targets uses a succinct delegation 1. the delegated_role argument is the name of some unrelated Metadata 1. that other Metadata is correctly signed by the keys defined in the succinct delegation the result would be a successful verification even though the Targets in question does not actually delegate to delegated_role. The impact is estimated to be low for following reasons: This cannot impact a TUF client that implements the client workflow as specified since the delegated role name is…Read More