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CVE-2025-33042: Schema to Shell: Unpacking the Apache Avro Code Injection Vulnerability

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Schema to Shell: Unpacking the Apache Avro Code Injection Vulnerability

Vulnerability ID: CVE-2025-33042
CVSS Score: 7.3
Published: 2026-02-13

Apache Avro, the serialization backbone of the big data ecosystem, contained a critical code injection vulnerability in its Java SDK. The flaw allowed attackers to weaponize Avro schemas—typically benign JSON definitions—to inject arbitrary Java code during the compilation phase. By manipulating metadata fields like documentation or annotations, a malicious schema could trick the SpecificCompiler into generating a Trojan horse Java class. This effectively turns a standard build process into a Remote Code Execution (RCE) vector, threatening developer workstations and CI/CD pipelines alike.

TL;DR

The Apache Avro Java SDK failed to sanitize schema metadata before generating Java source code. An attacker can craft a malicious schema that, when compiled by a developer or build server, injects and executes arbitrary Java code (RCE). Fixed in versions 1.11.5 and 1.12.1.

⚠️ Exploit Status: POC

Technical Details

  • CVE ID: CVE-2025-33042
  • CVSS v3.1: 7.3 (High)
  • CWE: CWE-94 (Code Injection)
  • Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
  • Impact: Remote Code Execution (Build-time or Run-time)
  • Fix Versions: 1.11.5, 1.12.1

Affected Systems

  • Apache Avro Java SDK < 1.11.5
  • Apache Avro Java SDK = 1.12.0
  • Projects using avro-maven-plugin < 1.11.5
  • Projects using avro-gradle-plugin < 1.11.5
  • Apache Avro Java SDK: <= 1.11.4 (Fixed in: 1.11.5)
  • Apache Avro Java SDK: 1.12.0 (Fixed in: 1.12.1)

Code Analysis

Commit: 84bc732

AVRO-4053: [Java] Validate specific compiler output

@@ -95,6 +95,8 @@
+    public static String escapeForJavadoc(String doc) {
+        if (doc == null) return null;
+        return doc.replace("*/", "*&#47;");
+    }
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Exploit Details

  • Hypothetical: Javadoc breakout via '*/' sequence allowing static initializer injection.

Mitigation Strategies

  • Input Validation
  • Output Encoding
  • Dependency Management
  • Build Isolation

Remediation Steps:

  1. Update org.apache.avro:avro and org.apache.avro:avro-compiler to version 1.11.5 or 1.12.1 immediately.
  2. If you use the avro-maven-plugin or avro-gradle-plugin, ensure the plugin version is also updated to match the patched SDK version.
  3. Audit your codebase for any Avro schemas (.avsc or .avpr files) that have been modified recently by untrusted contributors.
  4. As a defense-in-depth measure, run build pipelines in ephemeral, isolated containers with no access to sensitive secrets unless strictly necessary.

References

Read the full report for CVE-2025-33042 on our website for more details including interactive diagrams and full exploit analysis.

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