CVE-2024-3905: Tenda AC500 Buffer Overflow Vulnerability

CVE-2024-3905 Overview

CVE-2024-3905 is a stack-based buffer overflow vulnerability in the Tenda AC500 router running firmware version 2.0.1.9(1307). The flaw resides in the R7WebsSecurityHandler function processing requests to the /goform/execCommand endpoint. Attackers manipulate the password argument to trigger the overflow. The vulnerability is remotely exploitable over the network and requires low-level privileges. The exploit has been publicly disclosed under identifier VDB-261141. The vendor was contacted about this disclosure but did not respond.

Critical Impact
Authenticated remote attackers can trigger a stack-based buffer overflow in the router's web management interface, leading to potential remote code execution or device compromise.

Affected Products

Tenda AC500 router hardware
Tenda AC500 firmware version 2.0.1.9(1307)
Web management interface component R7WebsSecurityHandler

Discovery Timeline

2024-04-17 - CVE-2024-3905 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2024-3905

Vulnerability Analysis

The vulnerability exists in the R7WebsSecurityHandler function that services HTTP requests to /goform/execCommand on the Tenda AC500 web management interface. The function fails to validate the length of the password parameter before copying it into a fixed-size stack buffer. An attacker who supplies an oversized password value overflows the buffer and corrupts adjacent stack memory, including the saved return address.

The issue is classified under [CWE-121] Stack-Based Buffer Overflow and [CWE-787] Out-of-Bounds Write. On embedded MIPS or ARM devices such as the AC500, successful exploitation can redirect control flow to attacker-supplied data, resulting in arbitrary code execution in the context of the web server process, which typically runs as root.

The EPSS score is 1.773% with a percentile of 76.074, reflecting elevated exploitation likelihood relative to most CVEs. Public technical details are documented in the GitHub IoT Vulnerability Report.

Root Cause

The root cause is missing bounds checking on the password argument before it is copied into a stack-allocated buffer inside R7WebsSecurityHandler. The function trusts attacker-controlled HTTP input without enforcing a maximum length. Embedded router firmware from Tenda commonly relies on unsafe string operations such as strcpy or sprintf on user input, and this pattern is consistent with the observed flaw.

Attack Vector

Exploitation requires network access to the router's web management interface and a low-privilege authenticated session. The attacker sends a crafted HTTP POST request to /goform/execCommand with an oversized password field. The overflow corrupts the return address on the stack, allowing the attacker to divert execution to injected shellcode or a return-oriented programming (ROP) chain.

Because the AC500 lacks modern exploit mitigations found on desktop operating systems, successful memory corruption often translates directly into command execution on the device. Compromised routers can be pivoted into internal networks or enrolled into IoT botnets.

No verified proof-of-concept code is available in the provided data; refer to the GitHub IoT Vulnerability Report for technical write-up details.

Detection Methods for CVE-2024-3905

Indicators of Compromise

HTTP POST requests to /goform/execCommand containing abnormally long password parameter values.
Unexpected reboots, watchdog resets, or crashes of the httpd or web management process on the Tenda AC500.
Outbound connections from the router to unrecognized IP addresses following administrative-interface access.
New or unexplained changes to router configuration, DNS settings, or firewall rules.

Detection Strategies

Inspect web traffic destined for the router management interface for oversized parameter values in /goform/* endpoints.
Deploy network intrusion detection signatures that flag password fields exceeding expected length on Tenda AC500 devices.
Correlate router log anomalies with authentication events to identify low-privileged accounts triggering crashes.

Monitoring Recommendations

Restrict management interface exposure to trusted VLANs and monitor for any external access attempts.
Log and alert on repeated 5xx responses or session terminations from the router web server.
Track firmware integrity and configuration drift on all Tenda AC500 units in the environment.

How to Mitigate CVE-2024-3905

Immediate Actions Required

Disable remote (WAN-side) access to the Tenda AC500 web management interface immediately.
Restrict LAN-side access to /goform/execCommand to a dedicated management network or specific administrator hosts.
Rotate all router administrative credentials and remove unused low-privilege accounts that could satisfy the authentication requirement.
Isolate affected devices from sensitive network segments until a fix is available.

Patch Information

No vendor advisory or patch is referenced in the available data. According to the NVD entry, the vendor was contacted about this disclosure but did not respond. Organizations should treat the AC500 running firmware 2.0.1.9(1307) as unpatched and evaluate replacement with a supported device.

Workarounds

Place the router behind a network firewall that blocks inbound access to TCP ports used by the web management interface.
Enforce strong administrative passwords and disable any guest or low-privilege management accounts.
Consider replacing the AC500 with a vendor-supported device that receives active security updates.
Deploy network segmentation so that a compromised router cannot reach critical internal assets.

bash

# Example: block external access to router management interface with iptables
iptables -A INPUT -i wan0 -p tcp --dport 80 -j DROP
iptables -A INPUT -i wan0 -p tcp --dport 443 -j DROP
iptables -A FORWARD -d <router_ip> -p tcp --dport 80 -j DROP