CVE-2024-3366: Xuxueli Xxl-job RCE Vulnerability

CVE-2024-3366 Overview

A critical insecure deserialization vulnerability has been identified in Xuxueli xxl-job, a popular distributed task scheduling platform. This vulnerability affects the deserialize function within the file com/xxl/job/core/util/JdkSerializeTool.java of the Template Handler component. The flaw allows attackers to perform injection attacks through manipulation of serialized data, potentially leading to remote code execution on affected systems.

Critical Impact

This vulnerability enables network-based attacks without requiring authentication or user interaction, potentially allowing complete system compromise through insecure deserialization exploitation.

Affected Products

• Xuxueli xxl-job versions up to and including 2.4.1

Discovery Timeline

• 2024-04-06 - CVE-2024-3366 published to NVD
• 2025-07-18 - Last updated in NVD database

Technical Details for CVE-2024-3366

Vulnerability Analysis

CVE-2024-3366 represents a dangerous insecure deserialization vulnerability (CWE-502) combined with injection flaws (CWE-74). The vulnerability resides in the JdkSerializeTool.java file's deserialize function, which is responsible for converting serialized data back into Java objects. When this function processes untrusted input without proper validation, it creates an opportunity for attackers to inject malicious serialized objects that execute arbitrary code upon deserialization.

Java deserialization vulnerabilities are particularly dangerous because they can allow attackers to execute arbitrary code by crafting malicious serialized objects. When the application deserializes these objects, the embedded payload executes with the privileges of the application. In the context of xxl-job, which is used for distributed task scheduling, this could allow attackers to compromise job executors across an entire distributed infrastructure.

Root Cause

The root cause of this vulnerability is the lack of proper input validation and type checking in the deserialize function within JdkSerializeTool.java. The function appears to accept and deserialize data without implementing security controls such as object type whitelisting or input sanitization. This allows attackers to craft malicious serialized payloads that, when processed by the vulnerable function, result in arbitrary code execution or injection attacks.

Attack Vector

The vulnerability is exploitable over the network without requiring authentication or user interaction. An attacker can send specially crafted serialized data to the xxl-job application's Template Handler component. When this malicious data reaches the deserialize function in JdkSerializeTool.java, it is processed without adequate security checks, allowing the injected payload to execute.

The exploit has been disclosed to the public, as documented in the GitHub Issue Discussion and VulDB entry #259480. Attackers with knowledge of Java deserialization exploitation techniques can leverage common gadget chains to achieve remote code execution on vulnerable xxl-job instances.

Detection Methods for CVE-2024-3366

Indicators of Compromise

• Unusual network traffic patterns to xxl-job executor endpoints containing serialized Java objects
• Unexpected process spawning or command execution originating from the xxl-job application
• Anomalous log entries in xxl-job showing deserialization errors or unusual object instantiation
• Network connections from xxl-job services to unexpected external destinations

Detection Strategies

• Monitor for serialized Java object magic bytes (0xAC 0xED) in network traffic destined for xxl-job services
• Implement application-level logging to capture deserialization events and flag unusual class instantiation patterns
• Deploy network intrusion detection signatures that identify common Java deserialization exploitation payloads
• Use runtime application self-protection (RASP) solutions to detect and block deserialization attacks

Monitoring Recommendations

• Enable verbose logging for the xxl-job Template Handler component
• Configure security information and event management (SIEM) rules to correlate xxl-job related events with potential exploitation indicators
• Monitor system resource utilization for anomalies that may indicate post-exploitation activity
• Implement file integrity monitoring on xxl-job application directories

How to Mitigate CVE-2024-3366

Immediate Actions Required

• Upgrade xxl-job to a version newer than 2.4.1 that addresses this vulnerability
• Implement network segmentation to restrict access to xxl-job services from untrusted networks
• Apply Java deserialization filters using JEP 290 to restrict deserializable classes
• Review and audit all xxl-job executor configurations for exposure to untrusted networks

Patch Information

Organizations running xxl-job versions up to 2.4.1 should immediately review the project's GitHub repository for security updates and patched releases. Until an official patch is applied, implement the workarounds and hardening measures detailed below to reduce exposure to this vulnerability.

Workarounds

• Configure Java deserialization filters to whitelist only expected classes using -Djdk.serialFilter JVM parameter
• Implement network-level access controls to restrict xxl-job service access to trusted hosts only
• Consider replacing JDK serialization with safer alternatives such as JSON-based serialization where possible
• Deploy a Web Application Firewall (WAF) with rules to detect and block serialized Java object payloads

# Configuration example - JVM deserialization filter
# Add to xxl-job startup parameters to restrict deserialization
java -Djdk.serialFilter="!*" -jar xxl-job-admin.jar

# Alternative: Allow only specific safe classes
java -Djdk.serialFilter="com.xxl.job.core.biz.model.*;!*" -jar xxl-job-admin.jar