Package Instance

Apache Kafka Deserialization of Untrusted Data vulnerability
A possible security vulnerability has been identified in Apache Kafka.
This requires access to a alterConfig to the cluster resource, or Kafka Connect worker, and the ability to create/modify connectors on it with an arbitrary Kafka client SASL JAAS config
and a SASL-based security protocol, which has been possible on Kafka clusters since Apache Kafka 2.0.0 (Kafka Connect 2.3.0).
When configuring the broker via config file or AlterConfig command, or connector via the Kafka Kafka Connect REST API, an authenticated operator can set the `sasl.jaas.config`
property for any of the connector's Kafka clients to "com.sun.security.auth.module.LdapLoginModule", which can be done via the
`producer.override.sasl.jaas.config`, `consumer.override.sasl.jaas.config`, or `admin.override.sasl.jaas.config` properties.
This will allow the server to connect to the attacker's LDAP server
and deserialize the LDAP response, which the attacker can use to execute java deserialization gadget chains on the Kafka connect server.
Attacker can cause unrestricted deserialization of untrusted data (or) RCE vulnerability when there are gadgets in the classpath.

Since Apache Kafka 3.0.0, users are allowed to specify these properties in connector configurations for Kafka Connect clusters running with out-of-the-box
configurations. Before Apache Kafka 3.0.0, users may not specify these properties unless the Kafka Connect cluster has been reconfigured with a connector
client override policy that permits them.

Since Apache Kafka 3.9.1/4.0.0, we have added a system property ("-Dorg.apache.kafka.disallowed.login.modules") to disable the problematic login modules usage
in SASL JAAS configuration. Also by default "com.sun.security.auth.module.JndiLoginModule,com.sun.security.auth.module.LdapLoginModule" are disabled in Apache Kafka Connect 3.9.1/4.0.0. 

We advise the Kafka users to validate connector configurations and only allow trusted LDAP configurations. Also examine connector dependencies for 
vulnerable versions and either upgrade their connectors, upgrading that specific dependency, or removing the connectors as options for remediation. Finally,
in addition to leveraging the "org.apache.kafka.disallowed.login.modules" system property, Kafka Connect users can also implement their own connector
client config override policy, which can be used to control which Kafka client properties can be overridden directly in a connector config and which cannot.

Apache Kafka's SCRAM implementation Incorrectly Implements Authentication Algorithm
Incorrect Implementation of Authentication Algorithm in Apache Kafka's SCRAM implementation.

Issue Summary:
Apache Kafka's implementation of the Salted Challenge Response Authentication Mechanism (SCRAM) did not fully adhere to the requirements of RFC 5802 [1].
Specifically, as per RFC 5802, the server must verify that the nonce sent by the client in the second message matches the nonce sent by the server in its first message.
However, Kafka's SCRAM implementation did not perform this validation.

Impact:
This vulnerability is exploitable only when an attacker has plaintext access to the SCRAM authentication exchange. However, the usage of SCRAM over plaintext is strongly discouraged as it is considered an insecure practice [2]. Apache Kafka recommends deploying SCRAM exclusively with TLS encryption to protect SCRAM exchanges from interception [3].
Deployments using SCRAM with TLS are not affected by this issue.

How to Detect If You Are Impacted:
If your deployment uses SCRAM authentication over plaintext communication channels (without TLS encryption), you are likely impacted.
To check if TLS is enabled, review your server.properties configuration file for listeners property. If you have SASL_PLAINTEXT in the listeners, then you are likely impacted.

Fix Details:
The issue has been addressed by introducing nonce verification in the final message of the SCRAM authentication exchange to ensure compliance with RFC 5802.

Affected Versions:
Apache Kafka versions 0.10.2.0 through 3.9.0, excluding the fixed versions below.

Fixed Versions:
3.9.0
3.8.1
3.7.2

Users are advised to upgrade to 3.7.2 or later to mitigate this issue.

Recommendations for Mitigation:
Users unable to upgrade to the fixed versions can mitigate the issue by:
- Using TLS with SCRAM Authentication:
Always deploy SCRAM over TLS to encrypt authentication exchanges and protect against interception.
- Considering Alternative Authentication Mechanisms:
Evaluate alternative authentication mechanisms, such as PLAIN, Kerberos or OAuth with TLS, which provide additional layers of security.