CVE-2025-0848: Tenda A18 Buffer Overflow Vulnerability

CVE-2025-0848 Overview

A critical stack-based buffer overflow vulnerability has been identified in Tenda A18 wireless routers running firmware versions up to 15.13.07.09. This vulnerability exists in the SetCmdlineRun function within the HTTP POST Request Handler located at /goform/SetCmdlineRun. An attacker can exploit this flaw by manipulating the wpapsk_crypto5g argument, leading to a stack-based buffer overflow condition that can be triggered remotely over the network.

The vulnerability falls under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer) and CWE-787 (Out-of-bounds Write), indicating that input validation is insufficient when processing the wireless security configuration parameter.

Critical Impact

Remote attackers with low privileges can cause denial of service on affected Tenda A18 routers by sending maliciously crafted HTTP POST requests to the vulnerable endpoint. The exploit has been publicly disclosed, increasing the risk of exploitation.

Affected Products

• Tenda A18 Firmware version 15.13.07.09 and earlier
• Tenda A18 hardware devices running vulnerable firmware
• All network deployments utilizing affected Tenda A18 devices

Discovery Timeline

• 2025-01-30 - CVE-2025-0848 published to NVD
• 2025-03-06 - Last updated in NVD database

Technical Details for CVE-2025-0848

Vulnerability Analysis

This vulnerability represents a classic stack-based buffer overflow condition in embedded network device firmware. The SetCmdlineRun function fails to properly validate the length of input received through the wpapsk_crypto5g parameter before copying it to a fixed-size stack buffer. When an attacker supplies an oversized input value via an HTTP POST request, the function writes beyond the allocated buffer space on the stack, corrupting adjacent memory regions.

The network-accessible nature of this vulnerability is particularly concerning for IoT devices like the Tenda A18 router. These devices often operate with minimal security monitoring and may be deployed in environments where they are directly exposed to the internet or untrusted network segments.

Root Cause

The root cause stems from improper bounds checking in the firmware's HTTP request handler. The SetCmdlineRun function processes the wpapsk_crypto5g parameter—a value related to WPA-PSK wireless encryption configuration for the 5GHz band—without validating that the input length does not exceed the destination buffer's capacity. This lack of input validation allows an attacker to overflow the stack buffer, potentially overwriting return addresses or other critical stack data.

The vulnerability is classified under both CWE-119 and CWE-787, confirming that the firmware performs memory operations outside intended buffer boundaries, enabling out-of-bounds write conditions.

Attack Vector

The attack can be initiated remotely over the network by sending a specially crafted HTTP POST request to the /goform/SetCmdlineRun endpoint. The attacker must have low-level privileges (authenticated access to the router's web interface) but requires no user interaction to exploit the vulnerability.

An attacker would construct an HTTP POST request containing an excessively long value for the wpapsk_crypto5g parameter. When the vulnerable function processes this request, the oversized input overflows the stack buffer. Due to the nature of stack-based buffer overflows, this can corrupt the function's return address and other stack-resident variables, leading to denial of service conditions.

For detailed technical information regarding this vulnerability, refer to the GitHub Issue CVE Reference and VulDB entry #294011.

Detection Methods for CVE-2025-0848

Indicators of Compromise

• Unusual HTTP POST requests targeting /goform/SetCmdlineRun with abnormally large parameter values
• Router crashes or unexpected reboots coinciding with network activity to the administrative interface
• Web server logs showing repeated requests to the SetCmdlineRun endpoint with malformed data
• Unusual traffic patterns to the router's management interface from external or unauthorized sources

Detection Strategies

• Implement network-based intrusion detection rules to identify HTTP POST requests to /goform/SetCmdlineRun containing oversized wpapsk_crypto5g parameters
• Monitor for repeated connection attempts or unusual HTTP traffic patterns targeting the router's web interface
• Configure SIEM alerts for device availability issues or unexpected reboots of Tenda A18 devices
• Deploy deep packet inspection to analyze HTTP request payload sizes targeting known vulnerable endpoints

Monitoring Recommendations

• Enable logging on all network management interfaces and forward logs to a centralized SIEM platform
• Implement baseline monitoring for normal administrative traffic patterns to detect anomalies
• Set up availability monitoring with alerts for Tenda A18 device unavailability that may indicate exploitation attempts
• Review web access logs regularly for suspicious patterns targeting goform endpoints

How to Mitigate CVE-2025-0848

Immediate Actions Required

• Restrict network access to the router's administrative web interface to trusted management networks only
• Implement firewall rules to block external access to the Tenda A18 management interface
• Monitor the Tenda Official Website for firmware security updates addressing this vulnerability
• Consider network segmentation to isolate affected devices from critical network infrastructure
• Evaluate replacing affected devices with alternatives from vendors with stronger security update practices

Patch Information

As of the last NVD update on 2025-03-06, no vendor patch has been confirmed for this vulnerability. Organizations should monitor Tenda's official channels and the VulDB entry for updates regarding security patches. Given that the exploit has been publicly disclosed, applying patches immediately upon release is critical.

Workarounds

• Disable remote administration features and allow only local management access via wired connections
• Implement access control lists (ACLs) restricting which IP addresses can access the router's web interface
• Deploy a firewall or security appliance in front of the affected device to filter malicious requests
• Consider replacing the vulnerable device with a router that has active security support if no patch becomes available

# Example firewall rule to restrict access to router management interface
# Block external access to the management port (typically 80/443)
iptables -A INPUT -p tcp --dport 80 -s ! 192.168.1.0/24 -j DROP
iptables -A INPUT -p tcp --dport 443 -s ! 192.168.1.0/24 -j DROP

# Alternatively, restrict to specific management IP only
iptables -A INPUT -p tcp --dport 80 -s 192.168.1.100 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP