CVE-2024-0738: Garethhk Mldong RCE Vulnerability

CVE-2024-0738 Overview

A critical code injection vulnerability has been identified in the open-source mldong project version 1.0. This vulnerability affects the ExpressionEngine function within the file com/mldong/modules/wf/engine/model/DecisionModel.java. The flaw allows attackers to inject and execute arbitrary code through manipulation of input processed by the expression engine, potentially leading to complete system compromise.

Critical Impact

This vulnerability enables remote code execution through code injection, allowing unauthenticated attackers to execute arbitrary commands on affected systems with no user interaction required.

Affected Products

• Garethhk Mldong version 1.0
• Systems running mldong workflow engine with exposed DecisionModel.java functionality
• Applications integrating the vulnerable ExpressionEngine component

Discovery Timeline

• 2024-01-19 - CVE-2024-0738 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2024-0738

Vulnerability Analysis

The vulnerability exists within the expression evaluation mechanism of the mldong workflow engine. The ExpressionEngine function in DecisionModel.java processes user-supplied input without proper sanitization or validation, creating a code injection attack surface. When the workflow engine evaluates decision logic, it interprets expressions that can be manipulated to include malicious code payloads.

Expression engines that dynamically evaluate code are particularly susceptible to injection attacks when they fail to implement proper input validation and sandboxing. In this case, the affected function directly processes externally-supplied data, allowing attackers to craft malicious expressions that execute arbitrary Java code on the underlying system.

The attack can be initiated remotely without authentication, making it particularly dangerous for internet-facing deployments. Successful exploitation grants attackers the ability to read sensitive data, modify system configurations, and establish persistent access to compromised systems.

Root Cause

The root cause is classified as CWE-94 (Improper Control of Generation of Code - Code Injection). The ExpressionEngine function fails to properly sanitize or validate input before processing it through the expression evaluation mechanism. This allows untrusted data to be interpreted as executable code rather than being treated as data only.

The vulnerable component lacks input validation controls that would prevent malicious expressions from being evaluated. Without proper sandboxing or allowlist-based filtering, any expression syntax accepted by the engine can potentially be weaponized for code execution.

Attack Vector

The vulnerability is exploitable over the network without requiring authentication or user interaction. An attacker can target the workflow engine's expression evaluation endpoint by submitting crafted payloads that contain malicious code. The expression engine processes these payloads and executes the embedded code with the privileges of the application.

The attack flow typically involves identifying endpoints that accept expression input, crafting a payload that exploits the expression syntax to achieve code execution, and submitting the malicious request to trigger evaluation. Technical details regarding exploitation methodology have been publicly documented in the GitHub RCE Documentation.

Detection Methods for CVE-2024-0738

Indicators of Compromise

• Unusual process spawning from the Java application running mldong
• Unexpected network connections originating from the mldong workflow engine
• Log entries showing malformed or suspicious expression evaluation requests
• Evidence of command execution artifacts in system logs or temporary directories

Detection Strategies

• Monitor application logs for expression evaluation errors or unusual patterns in DecisionModel.java processing
• Implement Web Application Firewall (WAF) rules to detect and block code injection patterns targeting expression engines
• Deploy runtime application self-protection (RASP) to detect dynamic code execution attempts
• Utilize SentinelOne's behavioral AI to identify anomalous process activity indicative of successful exploitation

Monitoring Recommendations

• Enable verbose logging for the mldong workflow engine to capture all expression evaluation requests
• Configure alerting on any Java process spawning shell commands or making outbound connections
• Monitor for file system changes in application directories that may indicate post-exploitation activity
• Review network traffic for exfiltration patterns or command-and-control communications

How to Mitigate CVE-2024-0738

Immediate Actions Required

• Restrict network access to the mldong application to trusted sources only
• Implement input validation and sanitization on all expression engine inputs
• Deploy WAF rules to block known code injection patterns
• Consider taking the application offline until a patch is available or mitigations are verified

Patch Information

No vendor patch information is currently available in the enriched CVE data. Organizations should monitor the VulDB #251561 Resource Information and the official mldong repository for security updates. The VulDB #251561 Threat Report provides additional threat intelligence context for this vulnerability.

Workarounds

• Implement strict input validation to reject expressions containing potentially dangerous syntax or characters
• Deploy the application behind a reverse proxy with request filtering capabilities
• Use application-level access controls to restrict who can submit expressions for evaluation
• Consider implementing a sandboxed expression evaluation environment to limit the impact of successful injection

# Example: Restrict access to mldong application using iptables
# Allow only trusted IP ranges to access the application port
iptables -A INPUT -p tcp --dport 8080 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p tcp --dport 8080 -j DROP