CVE-2024-8076: Totolink T8 Buffer Overflow Vulnerability

CVE-2024-8076 Overview

CVE-2024-8076 is a buffer overflow vulnerability in the TOTOLINK AC1200 T8 router running firmware version 4.1.5cu.862_B20230228. The flaw resides in the setDiagnosisCfg function and can be triggered remotely by an authenticated attacker. Successful exploitation can corrupt memory and lead to arbitrary code execution or device compromise. The weakness is classified under [CWE-120] (Classic Buffer Copy Without Checking Size of Input). According to the NVD advisory, the vendor was contacted prior to public disclosure but did not respond.

Critical Impact

Remote attackers with low privileges can trigger memory corruption in the router's diagnosis configuration handler, enabling potential code execution and full device takeover.

Affected Products

• TOTOLINK AC1200 T8 router (hardware)
• TOTOLINK T8 firmware version 4.1.5cu.862_B20230228
• Deployments exposing the router web management interface to untrusted networks

Discovery Timeline

• 2024-08-22 - CVE-2024-8076 published to the National Vulnerability Database
• 2024-12-13 - Last updated in the NVD database

Technical Details for CVE-2024-8076

Vulnerability Analysis

The vulnerability exists in the setDiagnosisCfg function exposed through the TOTOLINK T8 router's management interface. The function accepts attacker-controlled input and copies it into a fixed-size stack or heap buffer without verifying the input length. When an oversized payload is supplied, the copy operation writes past the buffer boundary and overwrites adjacent memory regions.

The TOTOLINK T8 is a consumer wireless router, and the diagnosis configuration endpoint is reachable over the network. Because routers often run management services with elevated privileges, memory corruption in this handler can be leveraged to alter control flow within the device firmware. A public proof-of-concept demonstrating both command injection and a buffer overflow path against this endpoint is published in the GitHub PoC Repository.

Root Cause

The root cause is the absence of bounds checking on user-supplied parameters processed by setDiagnosisCfg. The handler trusts incoming length values and copies data into a fixed-size buffer using an unsafe string operation. This pattern is characteristic of [CWE-120], where untrusted input is written directly into a destination buffer without size validation.

Attack Vector

The attack is network-based and requires low privileges on the device interface, with no user interaction. An attacker on the same network segment, or on the internet if the management interface is exposed, sends a crafted HTTP request to the diagnosis configuration endpoint with an oversized parameter value. The malformed request triggers the overflow inside setDiagnosisCfg, corrupting adjacent memory and potentially redirecting execution. Additional technical context is available in the VulDB #275558 entry.

Detection Methods for CVE-2024-8076

Indicators of Compromise

• Unexpected reboots, crashes, or service restarts on TOTOLINK T8 devices following inbound HTTP POST requests to diagnosis configuration URIs
• HTTP requests targeting the setDiagnosisCfg handler containing unusually long parameter values
• Outbound connections from the router to unfamiliar hosts, indicating possible post-exploitation activity
• Newly created or modified accounts and configuration changes on the router that cannot be attributed to administrators

Detection Strategies

• Inspect HTTP traffic destined for router management interfaces for requests referencing setDiagnosisCfg with abnormally large payloads
• Alert on POST requests to TOTOLINK T8 admin endpoints originating from non-administrative network segments
• Correlate network telemetry with router syslog or SNMP data to surface crash and restart anomalies

Monitoring Recommendations

• Forward router logs and network flow data to a centralized analytics platform for long-term review
• Track authentication events on the router admin interface and flag brute-force or credential-stuffing patterns
• Monitor for scanning activity probing known TOTOLINK management paths from internal and external sources

How to Mitigate CVE-2024-8076

Immediate Actions Required

• Restrict access to the router's web management interface to trusted administrative hosts and VLANs only
• Disable remote (WAN-side) administration on affected TOTOLINK T8 devices
• Rotate administrative credentials and enforce strong, unique passwords on the device
• Inventory the environment for TOTOLINK T8 routers running firmware 4.1.5cu.862_B20230228 and prioritize them for replacement or isolation

Patch Information

No vendor patch is currently referenced in the NVD entry, and the vendor did not respond to disclosure attempts. Administrators should monitor the TOTOLink Official Website for firmware updates addressing the setDiagnosisCfg handler. Until a fix is published, treat affected devices as exposed and apply compensating network controls.

Workarounds

• Place affected routers behind a firewall and block inbound access to the management interface from untrusted networks
• Segment the router management plane onto a dedicated VLAN with strict access control lists
• Consider replacing unsupported or end-of-life TOTOLINK T8 devices with vendor-supported hardware that receives security updates

# Example: restrict TOTOLINK T8 admin interface access using an upstream firewall (iptables)
# Allow only the admin workstation 192.0.2.10 to reach the router management IP 10.0.0.1
iptables -A FORWARD -s 192.0.2.10 -d 10.0.0.1 -p tcp --dport 80 -j ACCEPT
iptables -A FORWARD -s 192.0.2.10 -d 10.0.0.1 -p tcp --dport 443 -j ACCEPT
iptables -A FORWARD -d 10.0.0.1 -p tcp --dport 80 -j DROP
iptables -A FORWARD -d 10.0.0.1 -p tcp --dport 443 -j DROP