CVE-2024-32937: Grandstream GXP2135 RCE Vulnerability

CVE-2024-32937 Overview

An OS command injection vulnerability exists in the CWMP SelfDefinedTimeZone functionality of Grandstream GXP2135 enterprise IP phones. This vulnerability allows a remote, unauthenticated attacker to execute arbitrary commands on the affected device by sending specially crafted network packets. The flaw stems from improper sanitization of user-supplied input in the CWMP (CPE WAN Management Protocol) configuration interface, specifically within the time zone configuration parameters.

Critical Impact

This vulnerability enables complete device compromise through unauthenticated remote command execution, potentially allowing attackers to take full control of affected Grandstream IP phones, intercept communications, pivot to internal networks, or render devices inoperable.

Affected Products

• Grandstream GXP2135 Firmware version 1.0.9.129
• Grandstream GXP2135 Firmware version 1.0.11.74
• Grandstream GXP2135 Firmware version 1.0.11.79

Discovery Timeline

• 2024-07-03 - CVE-2024-32937 published to NVD
• 2025-11-04 - Last updated in NVD database

Technical Details for CVE-2024-32937

Vulnerability Analysis

This command injection vulnerability (CWE-78) affects the CWMP SelfDefinedTimeZone functionality in Grandstream GXP2135 enterprise IP phones. CWMP, also known as TR-069, is a protocol commonly used for remote management of network devices. The vulnerability exists because the SelfDefinedTimeZone parameter does not properly validate or sanitize input before passing it to system shell commands.

When the device processes time zone configuration data through CWMP, user-controlled input is incorporated into shell commands without adequate filtering. An attacker can exploit this by injecting shell metacharacters and arbitrary commands into the time zone parameter, which are then executed with the privileges of the device's operating system.

The network-based attack vector with no authentication requirements makes this vulnerability particularly dangerous in enterprise environments where these IP phones are deployed. Successful exploitation could result in complete compromise of the device, including the ability to intercept voice communications, access stored credentials, and potentially pivot to other systems on the network.

Root Cause

The root cause of this vulnerability is insufficient input validation in the CWMP message handling code. The SelfDefinedTimeZone parameter accepts arbitrary string input that is subsequently passed to an underlying shell command without proper sanitization or escaping of shell metacharacters. This allows attackers to break out of the intended command context and inject additional commands for execution.

Attack Vector

The attack is conducted remotely over the network without requiring any authentication or user interaction. An attacker can exploit this vulnerability by:

1. Identifying a Grandstream GXP2135 device running a vulnerable firmware version
2. Crafting a malicious CWMP message containing command injection payloads in the SelfDefinedTimeZone parameter
3. Sending the specially crafted network packet sequence to the target device
4. The injected commands execute with system-level privileges on the device

The vulnerability can be triggered through a sequence of malicious packets targeting the CWMP service. Attackers can inject shell commands using common metacharacters such as semicolons, backticks, or command substitution syntax to achieve arbitrary command execution on the underlying operating system.

Detection Methods for CVE-2024-32937

Indicators of Compromise

• Unusual outbound network connections from Grandstream IP phones to unknown external IP addresses
• Unexpected process execution or resource utilization on affected devices
• Anomalous CWMP traffic patterns or malformed TR-069 messages targeting devices
• Evidence of shell command metacharacters (;, |, `, $()) in CWMP configuration parameters

Detection Strategies

• Monitor network traffic for suspicious CWMP/TR-069 communications containing potential injection patterns
• Implement IDS/IPS rules to detect command injection attempts in CWMP SelfDefinedTimeZone parameters
• Deploy network segmentation to isolate VoIP infrastructure and enable focused monitoring
• Review device logs for configuration changes or unexpected system commands

Monitoring Recommendations

• Enable logging on all Grandstream devices and forward logs to a centralized SIEM platform
• Establish baseline network behavior for IP phone communications and alert on anomalies
• Monitor for reconnaissance activity targeting CWMP services on port 7547 or configured TR-069 ports
• Implement network flow analysis to detect unusual traffic patterns from VoIP devices

How to Mitigate CVE-2024-32937

Immediate Actions Required

• Identify all Grandstream GXP2135 devices in your environment running firmware versions 1.0.9.129, 1.0.11.74, or 1.0.11.79
• Disable CWMP/TR-069 functionality if not required for device management
• Implement network segmentation to restrict access to IP phone management interfaces
• Apply firewall rules to block external access to CWMP services
• Monitor affected devices for signs of compromise while awaiting patches

Patch Information

Consult the Talos Intelligence Vulnerability Report for detailed technical information and remediation guidance. Contact Grandstream Networks directly for information regarding firmware updates that address this vulnerability. Ensure devices are updated to the latest available firmware version that resolves this security issue.

Workarounds

• Disable CWMP/TR-069 protocol on affected devices if remote management via this protocol is not essential
• Implement strict network access controls to limit which systems can communicate with IP phones
• Place VoIP devices on isolated VLANs with restricted ingress and egress filtering
• Configure firewall rules to block all CWMP traffic from untrusted networks
• Use alternative management methods such as local web interface or provisioning servers with proper access controls

If CWMP cannot be disabled due to operational requirements, ensure that only trusted management systems can access the CWMP service by implementing strict IP-based access control lists.