CVE-2024-6963: Tenda O3 Buffer Overflow Vulnerability

CVE-2024-6963 Overview

CVE-2024-6963 is a stack-based buffer overflow in the Tenda O3 wireless outdoor CPE running firmware version 1.0.0.10. The flaw resides in the formexeCommand function, where the cmdinput argument is copied without proper bounds checking. Attackers can trigger the overflow remotely over the network, corrupting stack memory on the device. The exploit has been publicly disclosed through VulDB entry 272117 and IoT vulnerability documentation on GitHub. The vendor was contacted about the issue but did not respond, leaving affected devices without an official patch.

Critical Impact
Remote attackers with low privileges can trigger memory corruption in the Tenda O3 router, potentially achieving arbitrary code execution and full device compromise.

Affected Products

Tenda O3 hardware version 2.0
Tenda O3 firmware version 1.0.0.10 (build 2478)
Deployments exposing the device web management interface to untrusted networks

Discovery Timeline

2024-07-22 - CVE-2024-6963 published to NVD with VulDB identifier 272117
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2024-6963

Vulnerability Analysis

The vulnerability affects the formexeCommand handler in the Tenda O3 web management binary. This function processes the cmdinput parameter supplied through an HTTP request. The handler copies the attacker-controlled string into a fixed-size stack buffer without validating its length. When cmdinput exceeds the destination buffer size, adjacent stack data — including saved return addresses — is overwritten.

The issue is categorized under [CWE-121] Stack-based Buffer Overflow and [CWE-787] Out-of-bounds Write. Exploitation can lead to control-flow hijacking on the MIPS-based device, giving attackers the ability to execute arbitrary commands with the privileges of the web service, typically root on embedded routers.

Root Cause

The root cause is the absence of length validation before a memory copy operation inside formexeCommand. The developer trusted client-supplied input from the cmdinput field, using an unsafe string routine to move data into a stack-allocated buffer. Because embedded router firmware often ships without stack canaries, ASLR, or non-executable stack protections, buffer corruption directly translates into exploitable conditions.

Attack Vector

An authenticated attacker on the same network as the device sends a crafted HTTP request to the web management interface with an oversized cmdinput value. The request reaches the formexeCommand handler, which copies the payload onto the stack and corrupts saved registers or the return address. Public documentation of the exploit is available in the GitHub IoT Vulnerability Documentation and the VulDB advisory.

No verified exploitation code is reproduced here. Refer to the technical write-up for parameter structure and payload construction details.

Detection Methods for CVE-2024-6963

Indicators of Compromise

HTTP POST requests targeting the formexeCommand endpoint on Tenda O3 management interfaces
Abnormally long cmdinput parameter values in web server logs, especially values exceeding several hundred bytes
Unexpected reboots, service crashes, or new outbound connections from the router following management-interface traffic
Presence of unfamiliar processes or shell sessions spawned from the router's HTTP daemon

Detection Strategies

Deploy network intrusion detection signatures that flag HTTP requests to formexeCommand containing oversized cmdinput payloads
Baseline normal administrative traffic to the router and alert on anomalous request sizes or non-administrator source addresses
Monitor for outbound connections from router management IP addresses to unknown external hosts, which may indicate post-exploitation activity

Monitoring Recommendations

Forward router syslog and web server access logs to a centralized SIEM for retention and correlation
Alert on repeated malformed HTTP requests to embedded device management endpoints
Track device firmware versions across the fleet to prioritize vulnerable Tenda O3 units for isolation

How to Mitigate CVE-2024-6963

Immediate Actions Required

Remove Tenda O3 devices running firmware 1.0.0.10 from untrusted network segments and block WAN-side access to the management interface
Restrict management access to a dedicated administrative VLAN using firewall access control lists
Rotate administrator credentials on affected devices to reduce the value of previously captured session tokens
Inventory Tenda O3 deployments and plan replacement with supported hardware where feasible

Patch Information

No vendor patch is available. According to the NVD entry, Tenda was contacted about the disclosure but did not respond. Organizations should treat affected units as unsupported and prioritize replacement or network-level isolation until the vendor releases a fix.

Workarounds

Disable remote management on the WAN interface and permit administrative HTTP access only from trusted internal hosts
Place the device behind an upstream firewall that filters HTTP requests targeting the formexeCommand path
Segment the router onto an isolated network so that a compromised device cannot pivot into production systems
Replace vulnerable units with actively maintained equipment when long-term operation is required

bash

# Example upstream firewall rule to restrict management access
# Allow HTTP management only from the admin subnet 10.10.0.0/24
iptables -A FORWARD -p tcp -s 10.10.0.0/24 -d <router_ip> --dport 80 -j ACCEPT
iptables -A FORWARD -p tcp -d <router_ip> --dport 80 -j DROP