CVE-2024-7331 Overview
CVE-2024-7331 is a buffer overflow vulnerability in the TOTOLINK A3300R router running firmware version 17.0.0cu.557_B20221024. The flaw resides in the UploadCustomModule function within /cgi-bin/cstecgi.cgi. Attackers manipulate the File argument to trigger a buffer overflow condition [CWE-120]. The vulnerability is remotely exploitable and the exploit has been publicly disclosed. TOTOLINK was contacted about the disclosure but did not respond. VulDB tracks this issue under identifier VDB-273254.
Critical Impact
Remote attackers with low-privilege access can trigger a buffer overflow in the router's CGI handler, potentially leading to arbitrary code execution or device compromise.
Affected Products
- TOTOLINK A3300R router (hardware)
- TOTOLINK A3300R firmware version 17.0.0cu.557_B20221024
- Devices exposing the /cgi-bin/cstecgi.cgi interface
Discovery Timeline
- 2024-08-01 - CVE-2024-7331 published to NVD
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2024-7331
Vulnerability Analysis
The vulnerability exists in the UploadCustomModule function exposed through the /cgi-bin/cstecgi.cgi binary on the TOTOLINK A3300R router. The CGI endpoint processes an HTTP-supplied File parameter and copies its contents into a fixed-size stack buffer without validating the input length. An attacker who submits an oversized File argument overflows the buffer boundary. This memory corruption can overwrite adjacent stack data, including saved return addresses. Successful exploitation may allow arbitrary code execution in the context of the CGI process, which typically runs with elevated privileges on embedded routers.
Root Cause
The root cause is missing bounds checking on user-controllable input in the UploadCustomModule handler. The function uses unsafe string-copy operations against a fixed-size destination buffer, characteristic of [CWE-120] classic buffer overflows. TOTOLINK firmware has a recurring pattern of insecure CGI parameter handling within cstecgi.cgi.
Attack Vector
Exploitation occurs over the network against the router's HTTP management interface. An authenticated attacker sends a crafted HTTP request to /cgi-bin/cstecgi.cgi invoking the UploadCustomModule action with an oversized File parameter. Devices exposing the management interface to untrusted networks face the highest risk. See the GitHub vulnerability documentation for reproduction details.
No verified exploitation code is published for inclusion here.
Refer to the linked GitHub documentation and VulDB entry for technical proof-of-concept details.
Detection Methods for CVE-2024-7331
Indicators of Compromise
- HTTP POST requests to /cgi-bin/cstecgi.cgi containing the UploadCustomModule action with abnormally large File parameter values.
- Unexpected reboots, crashes, or service restarts on TOTOLINK A3300R devices following inbound HTTP traffic.
- New or unauthorized administrative sessions on the router management interface.
Detection Strategies
- Inspect network traffic for oversized parameter payloads directed at the router's CGI endpoint.
- Correlate authentication events with anomalous HTTP request patterns targeting cstecgi.cgi.
- Deploy IDS/IPS signatures that flag buffer-overflow patterns in TOTOLINK CGI parameter handling.
Monitoring Recommendations
- Log all administrative HTTP requests to router management interfaces and forward them to a centralized SIEM.
- Monitor for repeated failed or malformed requests to /cgi-bin/cstecgi.cgi from a single source.
- Track firmware integrity and unexpected changes in device configuration state.
How to Mitigate CVE-2024-7331
Immediate Actions Required
- Restrict access to the router's web management interface to trusted internal networks only; never expose it to the public internet.
- Change default administrator credentials and enforce strong authentication on device management accounts.
- Segment vulnerable TOTOLINK A3300R devices from sensitive network zones until a vendor fix is available.
Patch Information
No vendor patch is available. The vendor was notified prior to public disclosure but did not respond. Organizations should treat firmware 17.0.0cu.557_B20221024 as unpatched and evaluate replacement or compensating controls. Track the VulDB entry #273254 for updates.
Workarounds
- Disable remote management (WAN-side administration) on the router.
- Place the device behind an upstream firewall that filters HTTP requests to /cgi-bin/cstecgi.cgi.
- Consider replacing the device with hardware from a vendor providing active security maintenance if no patch materializes.
# Example: block external access to the router management interface
iptables -A INPUT -p tcp --dport 80 -i <wan_interface> -j DROP
iptables -A INPUT -p tcp --dport 443 -i <wan_interface> -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
