Summary
Redisson vulnerable to Deserialization of Untrusted Data
Redisson is a Java Redis client that uses the Netty framework. Prior to version 3.22.0, some of the messages received from the Redis server contain Java objects that the client deserializes without further validation. Attackers that manage to trick clients into communicating with a malicious server can include especially crafted objects in its responses that, once deserialized by the client, force it to execute arbitrary code. This can be abused to take control of the machine the client is running in. Version 3.22.0 contains a patch for this issue.
Some post-fix advice is available. Do NOT use Kryo5Codec as deserialization codec, as it is still vulnerable to arbitrary object deserialization due to the setRegistrationRequired(false) call. On the contrary, KryoCodec is safe to use. The fix applied to SerializationCodec only consists of adding an optional allowlist of class names, even though making this behavior the default is recommended. When instantiating SerializationCodec please use the SerializationCodec(ClassLoader classLoader, Set<String> allowedClasses) constructor to restrict the allowed classes for deserialization.
Impact
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-2023-42809 has a CVSS score of 9.6 (Critical). The vector is network-reachable, no privileges required, and user interaction required. 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 (3.22.0); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
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. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Frequently Asked Questions
- What is CVE-2023-42809? CVE-2023-42809 is a critical-severity insecure deserialization vulnerability in org.redisson:redisson (maven), affecting versions < 3.22.0. It is fixed in 3.22.0. Untrusted serialized data is processed by a deserializer that can instantiate arbitrary objects or execute code as a side effect.
- How severe is CVE-2023-42809? CVE-2023-42809 has a CVSS score of 9.6 (Critical). 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.
- Which versions of org.redisson:redisson are affected by CVE-2023-42809? org.redisson:redisson (maven) versions < 3.22.0 is affected.
- Is there a fix for CVE-2023-42809? Yes. CVE-2023-42809 is fixed in 3.22.0. Upgrade to this version or later.
- Is CVE-2023-42809 exploitable, and should I be worried? Whether CVE-2023-42809 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
- What actually determines whether CVE-2023-42809 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.
- How do I fix CVE-2023-42809? Upgrade
org.redisson:redissonto 3.22.0 or later.