CVE-2024-39864: Apache CloudStack RCE Vulnerability

CVE-2024-39864 Overview

CVE-2024-39864 is a critical vulnerability affecting Apache CloudStack that allows unauthenticated remote code execution through an improperly initialized integration API service. The CloudStack integration API service is designed for internal portal integrations and testing purposes, typically running on port 8096 when explicitly configured. However, due to improper initialization logic, when the integration.api.port global setting is set to 0 (the default value intended to disable the service), the API service instead listens on a random port rather than being disabled.

This flaw enables attackers with access to the CloudStack management network to scan for the randomized integration API service port and exploit it to perform unauthorized administrative actions, ultimately achieving remote code execution on CloudStack managed hosts.

Critical Impact

Attackers can achieve complete compromise of CloudStack managed infrastructure including all confidentiality, integrity, and availability of managed hosts through unauthenticated API access.

Affected Products

• Apache CloudStack versions prior to 4.18.2.1
• Apache CloudStack versions prior to 4.19.0.2
• All CloudStack deployments with default integration.api.port configuration (set to 0)

Discovery Timeline

• 2024-07-05 - CVE CVE-2024-39864 published to NVD
• 2025-03-19 - Last updated in NVD database

Technical Details for CVE-2024-39864

Vulnerability Analysis

This vulnerability stems from a Code Injection flaw (CWE-94) in Apache CloudStack's integration API service initialization routine. The integration API is intended to provide an unauthenticated API endpoint for internal use cases such as portal integrations and testing environments. The design assumes this service is disabled by default when integration.api.port is set to 0 or a negative value.

The critical flaw occurs in the port binding logic. When the port value is set to 0, instead of disabling the service entirely, the underlying network socket initialization interprets this as a request to bind to an ephemeral port—a random available port assigned by the operating system. This behavior is consistent with standard socket programming conventions where port 0 signals dynamic port allocation, but it contradicts CloudStack's documented security model.

Once the service binds to a random port, the unauthenticated API becomes accessible to anyone who can reach the CloudStack management network. The API provides full administrative capabilities, including the ability to execute commands on managed hypervisor hosts, making this a complete infrastructure compromise scenario.

Root Cause

The root cause is improper initialization logic in the integration API service that fails to correctly handle the port value of 0. Rather than treating 0 as a disabled state, the code path proceeds with socket initialization, causing the operating system to assign an ephemeral port. This behavior violates the principle that the integration API should be completely disabled when not explicitly configured with a valid positive port number.

The initialization routine lacks a proper guard condition to exit early when the configured port value indicates the service should be disabled. Combined with the fact that the integration API operates without authentication by design, this creates a severe security exposure.

Attack Vector

An attacker with network access to the CloudStack management server can exploit this vulnerability through the following approach:

The attack begins with network reconnaissance against CloudStack management server hosts. Since the integration API binds to a random ephemeral port (typically in the range 32768-60999 on Linux systems), the attacker performs a port scan to identify listening services. Once the integration API port is discovered, the attacker can interact with it directly without authentication.

The unauthenticated API provides access to administrative functions that allow execution of arbitrary commands on CloudStack-managed hypervisor hosts. This enables the attacker to deploy malicious payloads, extract sensitive data from managed virtual machines, modify infrastructure configurations, or completely disable cloud services.

For technical details on the vulnerability mechanism, see the Apache CloudStack Security Advisory and the Openwall OSS Security Discussion.

Detection Methods for CVE-2024-39864

Indicators of Compromise

• Unexpected network connections to CloudStack management servers on high-numbered ephemeral ports (32768-60999)
• Unauthenticated API requests in CloudStack management server logs
• Unusual administrative actions or host commands executed without corresponding authenticated user sessions
• Port scanning activity targeting CloudStack management network segments

Detection Strategies

• Deploy network monitoring to detect port scanning activity against CloudStack management servers
• Configure firewall logging to identify connections to unexpected ports on management hosts
• Monitor CloudStack management server logs for API calls originating from untrusted sources
• Implement network segmentation monitoring to detect lateral movement attempts from the management network

Monitoring Recommendations

• Enable comprehensive logging for all API service activity on CloudStack management servers
• Monitor system processes for unexpected network listeners using netstat or ss command outputs
• Set up alerts for any service binding to ephemeral ports on CloudStack management hosts
• Review hypervisor host command execution logs for unauthorized or anomalous activity

How to Mitigate CVE-2024-39864

Immediate Actions Required

• Restrict network access to CloudStack management server hosts to only essential ports using firewall rules
• Audit current integration.api.port configuration values across all CloudStack deployments
• Implement network segmentation to isolate CloudStack management networks from general corporate networks
• Conduct a port scan of CloudStack management servers to identify any unexpectedly exposed services

Patch Information

Users are recommended to upgrade to Apache CloudStack version 4.18.2.1, 4.19.0.2, or later. These versions address the improper initialization logic by correctly handling port value 0 as a disabled state. The patched versions ensure the integration API service does not bind to any port when integration.api.port is set to 0 or negative values.

For detailed patch information, refer to the Apache CloudStack Security Advisory and the ShapeBlue Security Advisory.

Workarounds

• Configure integration.api.port to a negative value (e.g., -1) instead of 0 as a temporary workaround
• Implement strict firewall rules to allow only specific essential ports to CloudStack management servers
• Use network access control lists (ACLs) to restrict access to the management network to authorized administrators only
• Monitor for and block ephemeral port connections to management servers at the network perimeter

# Firewall configuration example - restrict access to CloudStack management server
# Allow only essential ports and block all others

# Example using iptables
iptables -A INPUT -p tcp --dport 8080 -s <trusted_network> -j ACCEPT
iptables -A INPUT -p tcp --dport 8250 -s <trusted_network> -j ACCEPT
iptables -A INPUT -p tcp --dport 9090 -s <trusted_network> -j ACCEPT
iptables -A INPUT -p tcp --dport 32768:60999 -j DROP