A possible arbitrary file read and SSRF vulnerability has been identified in Apache Kafka Client. Apache Kafka Clients accept configuration data for setting the SASL/OAUTHBEARER connection with the brokers, including "sasl.oauthbearer.token.endpoint.url" and "sasl.oauthbearer.jwks.endpoint.url". Apache Kafka allows clients to read an arbitrary file and return the content in the error log, or sending requests to an unintended location. In applications where Apache Kafka Clients configurations can be specified by an untrusted party, attackers may use the "sasl.oauthbearer.token.endpoint.url" and "sasl.oauthbearer.jwks.endpoint.url" configuratin to read arbitrary contents of the disk and environment variables or make requests to an unintended location. In particular, this flaw may be used in Apache Kafka Connect to escalate from REST API access to filesystem/environment/URL access, which may be undesirable in certain environments, including SaaS products.

Since Apache Kafka 3.9.1/4.0.0, we have added a system property ("-Dorg.apache.kafka.sasl.oauthbearer.allowed.urls") to set the allowed urls in SASL JAAS configuration. In 3.9.1, it accepts all urls by default for backward compatibility. However in 4.0.0 and newer, the default value is empty list and users have to set the allowed urls explicitly.

A security vulnerability has been identified in Apache Kafka. It affects all releases since 2.8.0. The vulnerability allows malicious unauthenticated clients to allocate large amounts of memory on brokers. This can lead to brokers hitting OutOfMemoryException and causing denial of service. Example scenarios: - Kafka cluster without authentication: Any clients able to establish a network connection to a broker can trigger the issue. - Kafka cluster with SASL authentication: Any clients able to establish a network connection to a broker, without the need for valid SASL credentials, can trigger the issue. - Kafka cluster with TLS authentication: Only clients able to successfully authenticate via TLS can trigger the issue. We advise the users to upgrade the Kafka installations to one of the 3.2.3, 3.1.2, 3.0.2, 2.8.2 versions.