CVE-2024-0573: Totolink LR1200GB Buffer Overflow Flaw

CVE-2024-0573 Overview

A critical stack-based buffer overflow vulnerability has been identified in the Totolink LR1200GB wireless router firmware version 9.1.0u.6619_B20230130. The vulnerability exists in the setDiagnosisCfg function within the /cgi-bin/cstecgi.cgi file, where improper handling of the ip argument allows attackers to trigger a stack-based buffer overflow. This vulnerability can be exploited remotely without authentication, potentially allowing complete device compromise.

Critical Impact

This stack-based buffer overflow vulnerability enables remote attackers to execute arbitrary code, potentially gaining full control over affected Totolink LR1200GB routers without requiring any authentication or user interaction.

Affected Products

• Totolink LR1200GB Firmware version 9.1.0u.6619_B20230130
• Totolink LR1200GB Hardware

Discovery Timeline

• January 16, 2024 - CVE-2024-0573 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2024-0573

Vulnerability Analysis

This vulnerability is classified as CWE-121 (Stack-based Buffer Overflow). The flaw resides in the setDiagnosisCfg function, which is accessible through the router's CGI interface at /cgi-bin/cstecgi.cgi. When processing the ip parameter, the function fails to properly validate the length of user-supplied input before copying it into a fixed-size stack buffer.

The network-accessible nature of this vulnerability means that attackers can exploit it remotely over the internet or local network without requiring any privileges or user interaction. The consequences are severe: successful exploitation could result in complete compromise of confidentiality, integrity, and availability of the affected device.

The exploit for this vulnerability has been publicly disclosed, significantly increasing the risk to unpatched devices. The vendor (Totolink) was contacted regarding this vulnerability but did not respond, leaving affected users without an official remediation path.

Root Cause

The root cause is insufficient input validation in the setDiagnosisCfg function when handling the ip argument. The function copies user-controlled data into a stack-allocated buffer without proper bounds checking, allowing an attacker to overwrite adjacent stack memory including the return address. This is a classic stack-based buffer overflow scenario resulting from unsafe string handling practices in embedded device firmware.

Attack Vector

The attack is network-based and targets the /cgi-bin/cstecgi.cgi endpoint on the router's web management interface. An attacker can craft a malicious HTTP request containing an oversized ip parameter value directed at the setDiagnosisCfg function. Since the vulnerability requires no authentication and no user interaction, an attacker with network access to the device's management interface can directly exploit this flaw. In scenarios where the router's web interface is exposed to the internet, remote exploitation from anywhere becomes possible.

The exploitation mechanism involves sending a specially crafted request with a malicious payload in the ip parameter that exceeds the expected buffer size. By carefully controlling the overflow data, an attacker can overwrite the saved return address on the stack and redirect program execution to attacker-controlled code, achieving arbitrary code execution with the privileges of the web server process (typically root on embedded devices).

Detection Methods for CVE-2024-0573

Indicators of Compromise

• Unusual or oversized HTTP requests targeting /cgi-bin/cstecgi.cgi with abnormally long ip parameter values
• Unexpected router reboots or crashes that may indicate exploitation attempts
• Unauthorized configuration changes on the router
• Suspicious outbound network connections originating from the router device

Detection Strategies

• Monitor HTTP traffic to the router's web interface for requests containing excessively long parameter values in the ip field
• Implement network intrusion detection rules to identify buffer overflow attack patterns targeting CGI endpoints
• Review router logs for evidence of exploitation attempts or unexpected service crashes
• Deploy network monitoring to detect anomalous traffic patterns from router devices

Monitoring Recommendations

• Implement network segmentation to isolate IoT and network infrastructure devices from critical systems
• Configure alerts for any unexpected changes to router configuration or firmware
• Monitor for unauthorized access attempts to the router's web management interface
• Establish baseline network behavior for the router and alert on deviations

How to Mitigate CVE-2024-0573

Immediate Actions Required

• Restrict access to the router's web management interface to trusted internal networks only
• Disable remote management features if not strictly required
• Implement firewall rules to block external access to the router's administrative interface on ports 80 and 443
• Consider replacing the affected device with a supported router from a vendor with active security maintenance

Patch Information

At the time of publication, no official patch has been released by Totolink. The vendor was contacted regarding this vulnerability but did not respond. Users should monitor the GitHub Vulnerability Report and VulDB entry for updates. Given the lack of vendor response, affected organizations should strongly consider migrating to alternative router solutions from vendors with demonstrated security support.

Workarounds

• Implement strict network access controls to limit exposure of the router's management interface
• Place the router behind a properly configured firewall that blocks unsolicited inbound connections to management ports
• Use VPN access for any required remote management rather than exposing the web interface directly
• Disable the web management interface entirely if management can be performed via other means (such as serial console)

# Example firewall rules to restrict management interface access
# Block external access to router management ports
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