CVE-2024-7584: Tenda I22 Buffer Overflow Vulnerability

CVE-2024-7584 Overview

CVE-2024-7584 is a buffer overflow vulnerability in the Tenda i22 wireless access point running firmware version 1.0.0.3(4687). The flaw resides in the formApPortalPhoneAuth function exposed through the /goform/apPortalPhoneAuth endpoint. Attackers can trigger the overflow by manipulating the data argument, leading to memory corruption on the device. The exploit is reachable over the network and has been publicly disclosed. According to the NVD entry, the vendor was contacted prior to disclosure but did not respond. The vulnerability is tracked under [CWE-120] (Classic Buffer Overflow).

Critical Impact

Remote attackers with low-privilege access can corrupt memory on Tenda i22 devices, potentially leading to denial of service or arbitrary code execution on affected access points.

Affected Products

• Tenda i22 hardware appliance
• Tenda i22 firmware version 1.0.0.3(4687)
• Networks relying on unpatched Tenda i22 access points for client connectivity

Discovery Timeline

• 2024-08-07 - CVE-2024-7584 published to NVD
• 2024-09-11 - Last updated in NVD database

Technical Details for CVE-2024-7584

Vulnerability Analysis

The vulnerability exists in the HTTP request handler formApPortalPhoneAuth, which processes phone authentication requests for the access point's captive portal. The handler reads the data parameter from the incoming request and copies it into a fixed-size stack buffer without enforcing length validation. Sending an oversized value overruns adjacent memory, corrupting saved registers and control structures on the stack.

Because Tenda i22 runs on an embedded Linux platform with limited memory protections, successful exploitation may allow attackers to crash the web management daemon or hijack execution flow. The endpoint is exposed through the device's HTTP interface, making remote attacks feasible whenever the management interface is reachable.

Root Cause

The root cause is missing bounds checking in formApPortalPhoneAuth when handling the data argument supplied to /goform/apPortalPhoneAuth. The function trusts attacker-controlled length and content, copying input into a fixed-size buffer. This pattern matches [CWE-120], where input copy size exceeds destination capacity.

Attack Vector

An attacker sends a crafted HTTP request to the /goform/apPortalPhoneAuth endpoint with an oversized data parameter. The request requires network reachability to the device's management interface and low-privilege authentication. Once the malformed payload is processed, the stack buffer overflows, producing a denial of service or potential code execution depending on the input layout. Public proof-of-concept material is referenced in the GitHub PoC Repository and VulDB #273864.

Detection Methods for CVE-2024-7584

Indicators of Compromise

• HTTP POST requests to /goform/apPortalPhoneAuth containing abnormally long data parameter values.
• Unexpected reboots, crashes, or restarts of the Tenda i22 web management daemon.
• Outbound connections from the access point to unfamiliar hosts following suspicious portal authentication traffic.

Detection Strategies

• Inspect web traffic destined for Tenda i22 management interfaces and alert on data parameter lengths exceeding expected phone authentication field sizes.
• Correlate device availability anomalies with preceding HTTP requests to /goform/ endpoints.
• Apply signature-based intrusion detection rules that flag malformed apPortalPhoneAuth requests on segments where Tenda i22 devices operate.

Monitoring Recommendations

• Forward access point syslog and HTTP daemon logs to a central log platform for retention and analysis.
• Baseline normal captive portal traffic patterns and alert on deviations in request size or frequency.
• Monitor for unauthorized configuration changes on Tenda i22 devices that could follow successful exploitation.

How to Mitigate CVE-2024-7584

Immediate Actions Required

• Restrict access to the Tenda i22 management interface to trusted administrative networks only.
• Disable the captive portal phone authentication feature if it is not required in your deployment.
• Place affected access points behind a network firewall that blocks untrusted access to /goform/ endpoints.
• Inventory all Tenda i22 units running firmware 1.0.0.3(4687) and prioritize them for replacement or isolation.

Patch Information

As of the last NVD update on 2024-09-11, the vendor has not published a security advisory or fixed firmware for CVE-2024-7584. The NVD record notes that Tenda did not respond to disclosure attempts. Administrators should monitor the Tenda support site for future firmware releases addressing this issue and consult the VulDB CTI ID #273864 entry for tracking updates.

Workarounds

• Block external access to TCP ports serving the Tenda i22 HTTP management interface at the perimeter.
• Segment Tenda i22 access points onto a dedicated management VLAN with strict ACLs limiting which hosts can reach /goform/apPortalPhoneAuth.
• Replace affected devices with vendor-supported alternatives if no patch becomes available and the captive portal feature is required.

# Example iptables rule restricting access to the Tenda i22 management interface
iptables -A FORWARD -p tcp -d <tenda_i22_ip> --dport 80 -s <admin_subnet> -j ACCEPT
iptables -A FORWARD -p tcp -d <tenda_i22_ip> --dport 80 -j DROP