CVE-2025-55423: ipTIME Router Command Injection RCE Flaw

CVE-2025-55423 Overview

A critical command injection vulnerability has been identified in multiple ipTIME router models affecting the upnp_relay() function. The vulnerability exists because the controlURL value, which is used to pass port-forwarding information to an upper router, is passed directly to the system() function without proper validation or sanitization. This allows remote attackers to execute arbitrary OS commands on affected devices.

Critical Impact

Remote attackers can achieve complete system compromise on affected ipTIME routers by injecting malicious commands through the unsanitized controlURL parameter, potentially leading to full device takeover, network infiltration, and persistent backdoor access.

Affected Products

• Multiple ipTIME router models (see GitHub Affected Products JSON for complete list)
• ipTIME routers with UPnP relay functionality enabled
• Devices running vulnerable firmware versions

Discovery Timeline

• 2026-01-20 - CVE-2025-55423 published to NVD
• 2026-01-21 - Last updated in NVD database

Technical Details for CVE-2025-55423

Vulnerability Analysis

This command injection vulnerability (CWE-94: Improper Control of Generation of Code) resides in the UPnP relay functionality of ipTIME routers. The vulnerable upnp_relay() function processes port-forwarding requests and communicates with upstream routers. When handling the controlURL parameter, the function fails to implement proper input validation or sanitization before passing the value to the system() function.

The network-accessible nature of this vulnerability, combined with the lack of authentication requirements and user interaction, makes it particularly dangerous. Attackers can exploit this flaw remotely without any privileges to execute arbitrary operating system commands with the same permissions as the router's web service process, typically root-level access on embedded devices.

Root Cause

The root cause of this vulnerability is improper input validation in the upnp_relay() function. The controlURL parameter, which is intended to contain a URL for UPnP communication with upstream routers, is directly concatenated into a command string and executed via the system() function. This classic command injection pattern allows attackers to break out of the intended command context by injecting shell metacharacters (such as ;, |, &, or backticks) followed by malicious commands.

Attack Vector

The attack vector is network-based, allowing remote exploitation without authentication. An attacker can craft a malicious UPnP request containing shell metacharacters and commands within the controlURL parameter. When the vulnerable upnp_relay() function processes this request, the injected commands are executed on the underlying operating system.

A typical attack scenario involves:

1. The attacker sends a crafted UPnP request to the target router
2. The malicious controlURL value contains embedded OS commands
3. The upnp_relay() function passes the unsanitized value to system()
4. The injected commands execute with router-level privileges

For detailed technical information about the exploitation mechanism, refer to the GitHub CVE-2025-55423 README.

Detection Methods for CVE-2025-55423

Indicators of Compromise

• Unusual outbound connections from router management interfaces to unknown external hosts
• Unexpected processes running on the router that are not part of normal firmware operation
• Modifications to router configuration files or persistent storage
• UPnP service logs showing malformed or suspicious controlURL values containing shell metacharacters

Detection Strategies

• Monitor network traffic for anomalous UPnP SOAP requests targeting the router's UPnP endpoint
• Implement IDS/IPS rules to detect command injection patterns in UPnP traffic (semicolons, pipes, backticks in URL parameters)
• Review router logs for failed or suspicious UPnP relay operations
• Deploy network behavioral analysis to identify post-exploitation activities such as reverse shells or data exfiltration

Monitoring Recommendations

• Enable verbose logging on affected ipTIME routers if available
• Configure SIEM rules to alert on potential command injection patterns in network traffic
• Implement network segmentation to isolate IoT and router devices from critical network segments
• Regularly audit router configurations for unauthorized changes

How to Mitigate CVE-2025-55423

Immediate Actions Required

• Check if your ipTIME router model is affected using the affected products list
• Disable UPnP functionality on affected routers until a patch is available
• Restrict network access to router management interfaces to trusted networks only
• Monitor for vendor firmware updates from ipTIME

Patch Information

Refer to the ipTIME Documentation Resource for official firmware updates and security advisories. Users should apply the latest firmware version as soon as it becomes available from the vendor.

Workarounds

• Disable UPnP relay functionality on affected devices to eliminate the attack surface
• Implement firewall rules to block external access to UPnP services (typically UDP port 1900 and related TCP ports)
• Place affected routers behind an additional firewall that can filter malicious UPnP requests
• Consider network segmentation to limit the potential impact of a compromised router

# Example: Block UPnP traffic at perimeter firewall (iptables)
iptables -A INPUT -p udp --dport 1900 -j DROP
iptables -A INPUT -p tcp --dport 5000 -j DROP
iptables -A INPUT -p tcp --dport 49152:65535 -j DROP