Hacker Insights is a series of blog posts providing an understanding of the tools, mindset, methodologies, and history of attackers – from overviews to in-depth technical explanations.

In this installment of Hacker Insights, we explore a critical deserialization vulnerability found in Oracle WebLogic. Serialization is the process of converting an object into a format suitable for storage or transmission. JSON and XML are common serialization formats used in web applications.

Deserialization, the reverse of serialization, becomes dangerous when applications accept and process untrusted serialized data. This can lead to severe security flaws, including remote code execution.

On April 25, 2019, researchers at KnownSec 404 disclosed a zero-day vulnerability (CVE-2019-2725) in Oracle WebLogic Server versions 10.3.6.0 and 12.1.3.0. This vulnerability exists in the wls9_async_response.war and wls-wsat.war components, enabling unauthenticated attackers to execute code remotely on affected systems.

Because WebLogic servers are often exposed to the internet, unpatched instances became immediate targets. This exploit has since been weaponized by threat actors to spread malware such as:

• Sodinokibi Ransomware: Delivered via PowerShell after successful exploitation.

• Muhstik Botnet: Executes DDoS and cryptojacking campaigns on compromised servers.

The scale of the threat is significant. At disclosure, over 36,000 WebLogic servers were exposed online. Nearly a month later, over 32,000 remained vulnerable.

Recommended Mitigations

• Apply Oracle’s official patch immediately to all WebLogic deployments.
• Restrict external access to administration panels and deployment interfaces.
• Implement a dedicated vulnerability management plan for Java-based platforms.
• Monitor network activity for signs of post-exploitation tools like PowerShell or abnormal CPU usage (common in cryptojacking).

If your organization hosts applications on WebLogic, this should serve as a wake-up call for implementing robust security controls around third-party software and serialization-based processes.

Want help assessing your environment or deploying WebLogic patches? Contact OCD Tech below.

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