CVE-2025-27818

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.

Untrusted serialized data is processed by a deserializer that can instantiate arbitrary objects or execute code as a side effect. Typical impact: arbitrary code execution or logic abuse.

CVE-2025-27818 has a CVSS score of 8.8 (High). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (3.9.1); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2025-27818? CVE-2025-27818 is a high-severity insecure deserialization vulnerability in org.apache.kafka:kafka_2.11 (maven), affecting versions >= 2.3.0, <= 2.4.1. It is fixed in 3.9.1. Untrusted serialized data is processed by a deserializer that can instantiate arbitrary objects or execute code as a side effect.
2. How severe is CVE-2025-27818? CVE-2025-27818 has a CVSS score of 8.8 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which packages are affected by CVE-2025-27818?
   • org.apache.kafka:kafka_2.11 (maven) (versions >= 2.3.0, <= 2.4.1)
   • org.apache.kafka:kafka_2.12 (maven) (versions >= 2.3.0, < 3.9.1)
   • org.apache.kafka:kafka_2.13 (maven) (versions >= 2.4.0, < 3.9.1)
4. Is there a fix for CVE-2025-27818? Yes. CVE-2025-27818 is fixed in 3.9.1. Upgrade to this version or later.
5. Is CVE-2025-27818 exploitable, and should I be worried? Whether CVE-2025-27818 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2025-27818 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2025-27818?
   • Upgrade org.apache.kafka:kafka_2.12 to 3.9.1 or later
   • Upgrade org.apache.kafka:kafka_2.13 to 3.9.1 or later