When API audit logging is enabled, the middleware reads the entire HTTP request body into memory without enforcing a size limit on login endpoints. Because the audit middleware is positioned earlier in the handler chain than Rancher's APIBodyLimitingHandler, the body-size cap (default 1 MiB) is bypassed for requests that pass through the audit copyReqBody path. An unauthenticated attacker can send arbitrarily large request bodies to the public login endpoints, causing the Rancher Manager server process to allocate memory proportional to the supplied body size. With just a few concurrent connections, this can exhaust available memory and terminate the Rancher Manager plane process, making the Rancher API and UI unavailable and interrupting management of all downstream clusters.

The endpoint /v3/import/{token}_{clusterId}.yaml retrieves the cluster object before validating the token. When a valid cluster ID references a cluster that has private registry secrets configured, a nil pointer dereference in pkg/systemtemplate/private_registry.go causes the request to return HTTP 502 Bad Gateway. For cluster IDs that do not exist, the endpoint returns HTTP 200. This observable difference in response codes constitutes a reliable enumeration oracle.

Rancher issues long-lived registration tokens to authenticate nodes and agents joining a downstream cluster. These tokens were stored and exposed in plaintext with no expiration, so a malicious user could obtain one either through the Rancher API, etcd, stored automation, or direct file access on a node, and could use it at any time to register a rogue node into the cluster.

A denial-of-service vulnerability was identified in multiple TLS listeners in Rancher. Both the cattle-cluster-agent component running in downstream clusters and the Rancher server itself use the dynamiclistener library to serve TLS traffic. Without an effective CN filter configured, dynamiclistener automatically appended to each serving certificate any hostname presented via Server Name Indication (SNI) in incoming TLS requests. An unauthenticated attacker with network access within the affected cluster could send a large number of TLS requests with distinct hostnames, causing the serving certificate to accumulate an unbounded number of Subject Alternative Names (SANs). Eventually, the certificate grows large enough that TLS handshakes fail with an excessive message size error, causing a denial of service on the affected listeners.