CVE-2024-0577: Totolink LR1200GB Buffer Overflow Flaw

CVE-2024-0577 Overview

A critical stack-based buffer overflow vulnerability has been identified in the Totolink LR1200GB router firmware version 9.1.0u.6619_B20230130. This vulnerability exists within the setLanguageCfg function located in the /cgi-bin/cstecgi.cgi file. Improper handling of the lang argument allows attackers to trigger a stack-based buffer overflow condition, potentially enabling remote code execution on affected devices.

The vulnerability can be exploited remotely without authentication, making it particularly dangerous for exposed network devices. The exploit details have been publicly disclosed, and the vendor (Totolink) was contacted about this issue but did not respond.

Critical Impact

Remote attackers can exploit this stack-based buffer overflow to execute arbitrary code on vulnerable Totolink LR1200GB routers, potentially gaining complete control over the device and compromising network security.

Affected Products

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

Discovery Timeline

• 2024-01-16 - CVE-2024-0577 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2024-0577

Vulnerability Analysis

This vulnerability is classified as CWE-121 (Stack-based Buffer Overflow). The flaw resides in the setLanguageCfg function within the CGI binary (/cgi-bin/cstecgi.cgi) responsible for handling language configuration on the router's web interface.

When processing the lang parameter, the function fails to properly validate the length of user-supplied input before copying it to a fixed-size stack buffer. This allows an attacker to supply an oversized value that overwrites adjacent stack memory, including the return address, enabling arbitrary code execution.

The vulnerability is particularly severe because it can be triggered remotely over the network without requiring any authentication or user interaction. An attacker with network access to the router's management interface can craft a malicious HTTP request to the vulnerable CGI endpoint.

Root Cause

The root cause is improper bounds checking in the setLanguageCfg function when processing the lang parameter. The function copies user-controlled input directly into a stack-allocated buffer without verifying that the input length does not exceed the buffer's capacity. This classic buffer overflow pattern allows attackers to corrupt stack memory and hijack program execution flow.

Attack Vector

The attack is initiated remotely over the network by sending a specially crafted HTTP request to the /cgi-bin/cstecgi.cgi endpoint on the router's web interface. The attacker manipulates the lang argument with an oversized payload designed to overflow the stack buffer and overwrite the return address.

By carefully crafting the overflow payload, an attacker can redirect execution to shellcode or existing code gadgets (ROP chain), achieving arbitrary code execution with the privileges of the web server process—typically root on embedded devices like routers.

Technical details and additional information about this vulnerability can be found in the GitHub vulnerability report and the VulDB entry #250793.

Detection Methods for CVE-2024-0577

Indicators of Compromise

• Unusual HTTP requests to /cgi-bin/cstecgi.cgi containing abnormally long lang parameter values
• Unexpected router reboots or crashes indicating potential exploitation attempts
• Modified firmware or configuration files on the router
• Unauthorized outbound connections from the router to unknown external IP addresses

Detection Strategies

• Monitor network traffic for HTTP requests targeting /cgi-bin/cstecgi.cgi with suspiciously long parameter values
• Implement intrusion detection rules to flag buffer overflow attack patterns in CGI requests to Totolink devices
• Deploy network-based anomaly detection to identify unusual traffic patterns from router management interfaces
• Review router access logs for repeated requests to the vulnerable endpoint

Monitoring Recommendations

• Enable logging on all network devices and centralize log collection for analysis
• Configure alerts for any access attempts to router administration interfaces from untrusted networks
• Implement network segmentation to isolate management interfaces from general network traffic
• Regularly audit firmware versions across all Totolink devices in the environment

How to Mitigate CVE-2024-0577

Immediate Actions Required

• Restrict access to the router's web management interface to trusted internal networks only
• Disable remote management features if not required
• Place affected devices behind a firewall with strict access controls
• Monitor for any updated firmware releases from Totolink that address this vulnerability
• Consider replacing affected devices with actively supported alternatives if no patch becomes available

Patch Information

At the time of this advisory, no official patch has been released by Totolink. The vendor was contacted regarding this disclosure but did not respond. Users should monitor the VulDB entry and Totolink's official support channels for any security updates.

Workarounds

• Disable the web management interface entirely if not needed for device administration
• Implement network-level access control lists (ACLs) to restrict access to the router's management interface to specific trusted IP addresses
• Use a VPN for remote management instead of exposing the management interface directly
• Deploy a web application firewall (WAF) in front of the management interface to filter malicious requests

# Example: Restrict management interface access using iptables on upstream firewall
# Block external access to router management port (adjust IP and port as needed)
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 80 -j DROP
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 443 -j DROP

# Allow only trusted management station
iptables -I FORWARD -s 192.168.1.100 -d 192.168.1.1 -p tcp --dport 80 -j ACCEPT