Overview
About vulnerability
Summary
Netty’s CorsHandler provides a shortCircuit() configuration designed to reject unauthorized cross-origin requests immediately, acting as a security control before requests reach the application. However, due to a logical operator error in the origin evaluation process, this protection can be entirely bypassed. An attacker can bypass the short-circuit mechanism by sending a request with an Origin: null header. This failure forwards unauthorized requests to the backend application, bypassing intended access controls.
Details
In io.netty.handler.codec.http.cors.CorsHandler#channelRead, the short-circuit logic relies on the configuration returned by getForOrigin(origin) to determine if an origin is authorized. If getForOrigin returns a configuration object, the short-circuit check (!(origin == null || config != null)) is bypassed, and the request proceeds to the backend.
The vulnerability is located in the getForOrigin method:
if (corsConfig.isNullOriginAllowed() || NULL_ORIGIN.equals(requestOrigin)) {
return corsConfig;
}
If an attacker sends Origin: null, NULL_ORIGIN.equals(requestOrigin) evaluates to true. The method returns the configuration object regardless of whether isNullOriginAllowed() was configured by the developer. The short-circuit is bypassed.
Impact
Applications relying on CorsHandler’s short-circuit feature to prevent unauthorized cross-origin requests from reaching their backend logic are completely exposed. The framework fails to enforce the developer’s intended access controls, allowing unauthorized requests to be processed.
Details
- Affected product:
- Apache CXF , Apache Hadoop , Apache Kafka , Apache Log4j , Apache Solr , Apache Spark , Eclipse Jetty , Netty , Spring , Wildfly , artemis , async-http-client , avro , aws-sdk-java , azure-sdk-for-java , bolt-connection-java , camel , cassandra-java-driver , corda , couchbase-jvm-clients , couchbase-jvm-clients-core-io , couchbase-jvm-clients-java-client , docker-java , elasticsearch , etcd4j , flink , flink-shaded , grpc-java , infinispan , java-driver , lettuce , logging-flume , micronaut-core , neo4j-java-driver , neo4j-ogm , netty , olingo-odata4 , pulsar , rabbitmq-stream-java-client , ribbon , rsocket-java , rxnetty , tika , vert.x , wildfly , zendesk-java-client , zookeeper
- Affected packages:
- netty-transport-classes-epoll @ 4.1.112.Final (+10135 more)