CVE-2025-33042: 
Java vulnerability analysis and mitigation

CVE-2025-33042 is a code injection vulnerability (CWE-94) in the Apache Avro Java SDK that allows unauthenticated remote attackers to execute arbitrary code by supplying malicious Avro schemas during record generation. It affects all versions of the Apache Avro Java SDK through 1.11.4 and version 1.12.0. The vulnerability was disclosed on February 12–13, 2026, via the oss-security mailing list and the Apache security advisory channel. It carries a CVSS v3.1 base score of 7.3 (High) (Red Hat Advisory, Openwall OSS-Sec).

The root cause is improper control of code generation (CWE-94) in the org.apache.avro:avro-compiler Maven package. When the Java SDK processes an Avro schema to generate Java record classes, it fails to adequately sanitize or validate schema-supplied input, allowing attacker-controlled content to be injected into the generated Java source code. Because code generation can be triggered by processing externally supplied schemas — for example, schemas received over a network — no authentication or user interaction is required. The vulnerability was tracked internally as AVRO-4053 and credited to finder Brant Eckert (Openwall OSS-Sec, GitHub Advisory).

Successful exploitation allows an unauthenticated network attacker to achieve arbitrary code execution within the Java application that processes the malicious schema, running as the application's service account. The CVSS v3.1 assessment reflects low confidentiality, integrity, and availability impacts on the vulnerable system, though the practical consequence of code execution can be far broader — including data exfiltration, lateral movement within the environment, or full system compromise depending on the application's privileges. Downstream products from IBM (Application Performance Management, Db2 on Cloud Pak for Data, Business Automation Insights) and Oracle (multiple product families) are also affected as they bundle the vulnerable library (Red Hat Advisory, IBM Advisory, Oracle CPU Apr 2026).

1. Identify target: Locate Java applications that use Apache Avro Java SDK versions ≤ 1.11.4 or 1.12.0 and accept Avro schemas from external or user-controlled sources (e.g., REST APIs, message queues, file uploads).
2. Craft malicious schema: Construct an Avro schema (JSON format) that embeds code injection payloads within schema fields such as record names, field names, or documentation strings that are interpolated unsanitized into generated Java source code.
3. Submit schema for processing: Deliver the malicious schema to the target application via whatever input channel it exposes — for example, an API endpoint that accepts schema definitions, a Kafka topic, or a file upload mechanism.
4. Trigger code generation: Cause the application to invoke the Avro SDK's code generation path (e.g., SpecificCompiler) against the attacker-supplied schema, which writes the injected payload into generated Java source.
5. Achieve code execution: The injected code executes within the JVM context of the application, enabling reverse shell establishment, data exfiltration, or further lateral movement (Openwall OSS-Sec, GitHub Advisory).

• Network: Unexpected inbound requests submitting large or structurally unusual Avro schema payloads (JSON with anomalous field names or documentation strings containing Java code fragments) to schema-processing endpoints.
• File System: Newly generated .java or .class files in temporary or build directories containing unexpected code constructs; unexpected JAR files or scripts written by the application process.
• Logs: Application logs showing Avro SpecificCompiler invocations with externally supplied schemas; Java compilation errors referencing injected code fragments; unexpected class loading events in JVM logs.
• Process: Unusual child processes spawned by the Java application process (e.g., bash, sh, curl, wget, python); outbound network connections from the application server to unknown external IPs.

Apache has released patched versions 1.12.1 and 1.11.5 of the Avro Java SDK that address this vulnerability; users should upgrade immediately (Openwall OSS-Sec, GitHub Advisory). As a temporary workaround where immediate patching is not feasible, avoid processing Avro schemas from untrusted or external sources until the upgrade is completed. Organizations using IBM products (APM, Db2 on Cloud Pak for Data, Business Automation Insights, EDB PGAI Hybrid Management) or Oracle products that bundle the affected library should apply the respective vendor patches (IBM Advisory, Oracle CPU Apr 2026). Red Hat has also issued a security advisory and errata (RHSA-2026:7109) for affected Red Hat products (Red Hat Advisory).

Red Hat, IBM, and Oracle all issued advisories acknowledging the vulnerability in their products that bundle the Apache Avro Java SDK (Red Hat Advisory, IBM Advisory, Oracle CPU Apr 2026). The Quarkus project released version 3.27.3 to address the issue in its dependency chain. Community coverage appeared on dev.to and security blogs shortly after disclosure, with articles such as "Schema to Shell: Unpacking the Apache Avro Code Injection Vulnerability" highlighting the supply-chain risk for Java ecosystems. Social media activity was moderate, with early mentions on Bluesky and security aggregators within hours of the advisory publication.