Apache Kafka: Broker does not enforce JWT issuer and audience validation for SASL/OAUTHBEARER by default

DescriptionNVD

A Kafka broker that authenticates clients with SASL/OAUTHBEARER using the bundled JWKS-backed validator always verifies the JWT signature, but two further checks are only performed when explicitly configured: The issuer (iss) claim is verified only when sasl.oauthbearer.expected.issuer is set. When it is unset, a validly-signed token carrying the expected audience is accepted regardless of which issuer minted it. An audience (aud) claim is required only when sasl.oauthbearer.expected.audience is set. When it is unset, a validly-signed token that omits the aud claim is accepted. (A token that carries an aud claim is still rejected when no expected audience is configured.) Both options default to unset and have been documented as optional (Importance LOW) since KIP-768 (3.1.0). Impact: The exposure is realizable mainly in deployments whose JWKS endpoint serves signing keys for more than one issuer (a multi-tenant identity provider, an aggregated/shared JWKS, or shared signing keys): a token minted for a different issuer, or a token lacking an audience, may be accepted to authenticate — potentially as a higher-privileged principal. In a single-issuer deployment where the

• NVD entrynvd.nist.gov
• Vendor advisorykafka.apache.org
• CVE recordcve.org