CVE-2024-7336 Overview
CVE-2024-7336 is a buffer overflow vulnerability in the TOTOLINK EX200 wireless range extender running firmware version 4.0.3c.7646_B20201211. The flaw resides in the loginauth function of the /cgi-bin/cstecgi.cgi binary. Attackers can manipulate the http_host argument to overflow a fixed-size buffer. The vulnerability is exploitable remotely and public exploit details have been disclosed. The vendor was contacted before public disclosure but did not respond. This weakness is classified under CWE-120: Buffer Copy without Checking Size of Input.
Critical Impact
Remote attackers can trigger memory corruption in the router's authentication handler, potentially achieving arbitrary code execution or denial of service on affected TOTOLINK EX200 devices.
Affected Products
- TOTOLINK EX200 hardware device
- TOTOLINK EX200 firmware version 4.0.3c.7646_B20201211
- /cgi-bin/cstecgi.cgi CGI binary (loginauth function)
Discovery Timeline
- 2024-08-01 - CVE-2024-7336 published to the National Vulnerability Database
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2024-7336
Vulnerability Analysis
The vulnerability affects the loginauth function invoked through the /cgi-bin/cstecgi.cgi handler on the TOTOLINK EX200. When a client submits an HTTP request to the authentication endpoint, the CGI parses the http_host argument and copies its contents into a fixed-length stack or heap buffer without validating the input length. Because the request originates from an unauthenticated network-facing interface, attackers can send oversized http_host values to corrupt adjacent memory. Public technical documentation of the issue is available in the IoT vulnerability writeup on GitHub and the VulDB CVE Analysis #273259.
Root Cause
The root cause is a classic unbounded string copy in the CGI request handler. The loginauth routine trusts the length of the attacker-controlled http_host HTTP header argument and performs a copy operation without applying a size check. This CWE-120 pattern is common in embedded MIPS/ARM router firmware where strcpy, sprintf, or memcpy calls operate on user-supplied HTTP fields.
Attack Vector
An attacker with network reachability to the router's management interface can send a crafted HTTP request to /cgi-bin/cstecgi.cgi with an oversized http_host argument. The overflow occurs during request parsing, before authentication succeeds, making the endpoint remotely exploitable. Successful exploitation can crash the httpd process or, with a properly aligned payload, redirect execution flow on the embedded device. See VulDB Details #273259 for additional artifact references.
No verified proof-of-concept code is included here. Refer to the linked GitHub IoT vulnerability documentation for technical reproduction details.
Detection Methods for CVE-2024-7336
Indicators of Compromise
- Unexpected reboots or httpd crash loops on TOTOLINK EX200 devices
- HTTP requests to /cgi-bin/cstecgi.cgi containing abnormally long http_host header values
- Outbound connections from the extender to unknown IP addresses following a suspicious HTTP request
- Configuration changes on the device not initiated by an administrator
Detection Strategies
- Inspect network traffic for HTTP requests targeting /cgi-bin/cstecgi.cgi with http_host parameter lengths exceeding typical hostname sizes (for example, greater than 256 bytes).
- Deploy IDS/IPS signatures that flag oversized HTTP header fields destined for TOTOLINK management ports.
- Correlate router syslog events showing repeated CGI process restarts with inbound HTTP activity from the same source.
Monitoring Recommendations
- Forward router logs to a central log platform and alert on httpd or cstecgi process termination events.
- Monitor DHCP and ARP tables for TOTOLINK EX200 devices to maintain an inventory of exposed hardware.
- Restrict and log all administrative access attempts to the extender's web interface.
How to Mitigate CVE-2024-7336
Immediate Actions Required
- Remove the TOTOLINK EX200 management interface from any untrusted network segment, including guest Wi-Fi and the public internet.
- Place affected devices behind a firewall that blocks inbound HTTP/HTTPS to the router except from a dedicated administrative host.
- Rotate any credentials configured on or reused with the device, as an unauthenticated attacker may have reached the CGI.
- Evaluate replacement of the EX200 with a currently supported extender, since the vendor did not respond to disclosure.
Patch Information
No vendor patch has been published for CVE-2024-7336. According to the CVE record, TOTOLINK was contacted prior to disclosure but did not respond. Administrators should treat firmware 4.0.3c.7646_B20201211 as end-of-support for this issue and rely on compensating controls until an official update is released. Track vendor advisories through the VulDB CVE Analysis #273259 entry.
Workarounds
- Disable remote management (WAN-side administration) on the device.
- Restrict LAN-side access to the web interface using ACLs or a management VLAN.
- Segment IoT and consumer network hardware away from workstations and servers to limit blast radius.
- Consider decommissioning the device if it cannot be isolated from untrusted clients.
# Example firewall rule to restrict access to the TOTOLINK EX200 web UI
# Replace 192.0.2.10 with the admin workstation and 10.0.0.5 with the router IP
iptables -A FORWARD -s 192.0.2.10 -d 10.0.0.5 -p tcp --dport 80 -j ACCEPT
iptables -A FORWARD -d 10.0.0.5 -p tcp --dport 80 -j DROP
iptables -A FORWARD -d 10.0.0.5 -p tcp --dport 443 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
