CVE-2024-2813: Tenda AC15 Buffer Overflow Vulnerability

CVE-2024-2813 Overview

CVE-2024-2813 is a stack-based buffer overflow [CWE-121] in the Tenda AC15 wireless router running firmware version 15.03.20_multi. The flaw resides in the form_fast_setting_wifi_set function, which handles requests to the /goform/fast_setting_wifi_set endpoint. An unauthenticated attacker can overflow the stack by supplying an oversized ssid argument over the network. The exploit details have been disclosed publicly under VulDB identifier VDB-257668. According to VulDB, the vendor was contacted before disclosure but did not respond.

Critical Impact
Remote, unauthenticated attackers can corrupt the router's stack via the ssid parameter, enabling denial of service and potential arbitrary code execution on the device.

Affected Products

Tenda AC15 hardware router
Tenda AC15 firmware version 15.03.20_multi
Deployments exposing the /goform/fast_setting_wifi_set web management endpoint

Discovery Timeline

2024-03-22 - CVE-2024-2813 published to the National Vulnerability Database (NVD)
2024-11-21 - Last updated in NVD database

Technical Details for CVE-2024-2813

Vulnerability Analysis

The vulnerability resides in the form_fast_setting_wifi_set handler exposed by the Tenda AC15 web management interface at /goform/fast_setting_wifi_set. This endpoint processes the Wi-Fi quick-setup form and reads the user-supplied ssid parameter directly into a fixed-size stack buffer. Because the firmware performs no length validation on the incoming value, an oversized ssid string overflows the local buffer and overwrites adjacent stack memory, including the saved return address.

Successful exploitation can crash the httpd process, reboot the device, or lead to arbitrary code execution in the context of the web server, which typically runs with root privileges on consumer routers. Because the management interface is reachable over the network without authentication in many default configurations, the vulnerability provides a direct path to full device compromise.

Root Cause

The root cause is an unbounded copy of attacker-controlled input into a stack buffer inside form_fast_setting_wifi_set. The handler trusts the length of the ssid HTTP POST parameter and uses an unsafe string copy without bounds checking, matching the [CWE-121] stack-based buffer overflow pattern common in MIPS-based consumer router firmware.

Attack Vector

The attack vector is network-based and requires no authentication or user interaction. An attacker reachable to the router's management interface sends a crafted HTTP POST request to /goform/fast_setting_wifi_set with an ssid value long enough to overrun the destination buffer. On internet-exposed devices, the attack is reachable directly from the WAN. On LAN-only deployments, any device on the local network, including a compromised IoT endpoint or a guest Wi-Fi client, can trigger the flaw.

A public technical write-up describing the request structure is available in the GitHub IoT Vulnerability Resource and the VulDB entry for VDB-257668.

Detection Methods for CVE-2024-2813

Indicators of Compromise

HTTP POST requests to /goform/fast_setting_wifi_set containing abnormally long ssid parameter values
Unexpected reboots, httpd crashes, or watchdog resets on Tenda AC15 devices
New or unknown administrative sessions originating from the WAN interface following malformed requests

Detection Strategies

Inspect web traffic destined for the router management interface and alert on ssid field lengths that exceed expected SSID limits (32 bytes per IEEE 802.11)
Deploy network IDS signatures matching POST requests to /goform/fast_setting_wifi_set with payload sizes inconsistent with legitimate setup flows
Correlate router crash or reboot events with preceding HTTP traffic to the fast_setting_wifi_set endpoint

Monitoring Recommendations

Log all administrative HTTP requests to the AC15 management plane and forward them to a centralized SIEM for analysis
Track outbound connections from the router itself, which may indicate post-exploitation command-and-control activity
Monitor for unauthorized firmware modifications or configuration changes through periodic integrity checks

How to Mitigate CVE-2024-2813

Immediate Actions Required

Disable remote (WAN-side) administration on Tenda AC15 routers until a fixed firmware release is available
Restrict access to the LAN management interface to a dedicated administrative VLAN or trusted host list
Replace end-of-support or unresponsive vendor hardware in high-risk environments with actively maintained equipment

Patch Information

No vendor patch is currently referenced in the CVE record. VulDB notes that the vendor was contacted before disclosure but did not respond. Affected operators should track the Tenda support channels for firmware updates beyond 15.03.20_multi and apply any release that explicitly addresses the form_fast_setting_wifi_set handler.

Workarounds

Block external access to TCP ports used by the router web UI (typically 80/443) at the upstream firewall
Place the router management interface behind a VPN and require authenticated access for any configuration changes
Segment IoT and guest networks from the management VLAN to limit lateral access to /goform/fast_setting_wifi_set from compromised clients
Monitor and rate-limit HTTP POSTs to the router's /goform/ endpoints to disrupt exploitation attempts

bash

# Example upstream firewall rule (iptables) to block WAN-side access to the router web UI
# Replace ROUTER_WAN_IP with the AC15 WAN address
iptables -A FORWARD -p tcp -d ROUTER_WAN_IP --dport 80  -j DROP
iptables -A FORWARD -p tcp -d ROUTER_WAN_IP --dport 443 -j DROP