CVE-2021-44521

Apache Cassandra vulnerable to Code Injection due to unsafe configuration

When running Apache Cassandra with the following configuration: enable_user_defined_functions: true enable_scripted_user_defined_functions: true enable_user_defined_functions_threads: false it is possible for an attacker to execute arbitrary code on the host. The attacker would need to have enough permissions to create user defined functions in the cluster to be able to exploit this. Note that this configuration is documented as unsafe, and will continue to be considered unsafe after this CVE.

Untrusted input is evaluated as executable code within the application's runtime environment. Typical impact: arbitrary code execution within the application's privilege context.

CVE-2021-44521 has a CVSS score of 9.1 (Critical). The vector is network-reachable, high 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 (3.0.26, 3.11.12, 4.0.2); upgrading removes the vulnerable code path.

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1. What is CVE-2021-44521? CVE-2021-44521 is a critical-severity code injection vulnerability in org.apache.cassandra:cassandra-all (maven), affecting versions < 3.0.26. It is fixed in 3.0.26, 3.11.12, 4.0.2. Untrusted input is evaluated as executable code within the application's runtime environment.
2. How severe is CVE-2021-44521? CVE-2021-44521 has a CVSS score of 9.1 (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.
3. Which versions of org.apache.cassandra:cassandra-all are affected by CVE-2021-44521? org.apache.cassandra:cassandra-all (maven) versions < 3.0.26 is affected.
4. Is there a fix for CVE-2021-44521? Yes. CVE-2021-44521 is fixed in 3.0.26, 3.11.12, 4.0.2. Upgrade to this version or later.
5. Is CVE-2021-44521 exploitable, and should I be worried? Whether CVE-2021-44521 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-2021-44521 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-2021-44521?
   • Upgrade org.apache.cassandra:cassandra-all to 3.0.26 or later
   • Upgrade org.apache.cassandra:cassandra-all to 3.11.12 or later
   • Upgrade org.apache.cassandra:cassandra-all to 4.0.2 or later

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