CVE-2024-7585: Tenda I22 Buffer Overflow Vulnerability

CVE-2024-7585 Overview

CVE-2024-7585 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 formApPortalWebAuth function handling requests to /goform/apPortalAuth. Attackers can trigger memory corruption by manipulating the webUserName and webUserPassword arguments. The vulnerability is remotely exploitable across the network and the exploit details have been publicly disclosed. Tenda did not respond to disclosure attempts, leaving the affected firmware without an official patch. The weakness maps to [CWE-120], classic buffer copy without checking input size.

Critical Impact

Remote attackers with low-privilege access can corrupt memory in the captive portal authentication handler, leading to potential code execution or denial of service on the device.

Affected Products

• Tenda i22 firmware version 1.0.0.3(4687)
• Tenda i22 wireless access point hardware
• Deployments exposing the /goform/apPortalAuth endpoint to untrusted networks

Discovery Timeline

• 2024-08-07 - CVE-2024-7585 published to NVD
• 2024-09-11 - Last updated in NVD database

Technical Details for CVE-2024-7585

Vulnerability Analysis

The vulnerability resides in the formApPortalWebAuth function within the Tenda i22 web management interface. This function processes captive portal authentication requests sent to the /goform/apPortalAuth endpoint. The handler accepts the webUserName and webUserPassword parameters from HTTP requests without validating their length before copying them into fixed-size stack buffers. Sending oversized values for either parameter overflows the destination buffer and corrupts adjacent stack memory, including saved return addresses on MIPS-based embedded firmware. Successful exploitation can compromise confidentiality, integrity, and availability of the affected device.

Root Cause

The root cause is missing bounds checking on user-supplied input in a CGI-style form handler. The firmware uses unsafe string copy operations to move the webUserName and webUserPassword values into fixed-size buffers. Tenda firmware historically relies on strcpy and sprintf patterns in its httpd binary, which do not enforce destination buffer limits.

Attack Vector

The attack is network-based and requires low privileges, typically network reachability to the device management interface. An attacker sends a crafted HTTP POST request to /goform/apPortalAuth containing an oversized webUserName or webUserPassword field. No user interaction is required. Devices exposing the management interface to wireless clients or the internet face the highest risk. Public proof-of-concept material is available in the BeaCox IoT_vuln GitHub repository.

The vulnerability manifests in the boundary handling logic of the portal authentication function. See the VulDB entry 273865 for additional technical analysis and reproduction details.

Detection Methods for CVE-2024-7585

Indicators of Compromise

• HTTP POST requests to /goform/apPortalAuth containing unusually long webUserName or webUserPassword values
• Unexpected reboots, crashes, or httpd process restarts on Tenda i22 access points
• Unrecognized administrative sessions or configuration changes following portal authentication attempts
• Outbound connections from access points to unfamiliar hosts following suspicious portal requests

Detection Strategies

• Inspect HTTP request bodies at the network perimeter for parameter lengths exceeding reasonable thresholds against the /goform/apPortalAuth URI
• Deploy IDS signatures matching long string payloads in the webUserName and webUserPassword POST fields
• Correlate web request anomalies with device health telemetry such as restart events or watchdog triggers

Monitoring Recommendations

• Forward syslog and SNMP traps from Tenda i22 devices to a centralized logging platform for crash and reboot analysis
• Baseline normal captive portal authentication traffic volume and parameter sizes to highlight outliers
• Alert on repeated authentication failures or malformed requests targeting /goform/ endpoints

How to Mitigate CVE-2024-7585

Immediate Actions Required

• Remove the Tenda i22 management interface from untrusted networks and restrict access to a dedicated management VLAN
• Block external access to /goform/apPortalAuth at perimeter firewalls and upstream routers
• Disable the captive portal feature on affected devices if it is not in active use
• Evaluate replacement of Tenda i22 hardware with vendor-supported alternatives given the absence of vendor response

Patch Information

No official patch is available. According to the CVE record, the vendor was contacted before public disclosure but did not respond. Organizations operating Tenda i22 devices on firmware 1.0.0.3(4687) must rely on compensating controls until a vendor fix is released. Monitor the VulDB advisory for updates.

Workarounds

• Place affected access points behind a firewall that filters HTTP requests to the /goform/apPortalAuth path
• Enforce strict ACLs limiting management plane access to known administrative IP addresses
• Disable remote management features and require on-site or VPN access for configuration changes
• Segment guest wireless traffic so clients cannot reach the device management interface

# Example iptables rule to block external access to the vulnerable endpoint
iptables -A FORWARD -p tcp --dport 80 -d <tenda_i22_ip> \
  -m string --algo bm --string "/goform/apPortalAuth" -j DROP

# Restrict management access to a trusted subnet only
iptables -A FORWARD -p tcp --dport 80 -d <tenda_i22_ip> \
  ! -s 10.10.0.0/24 -j DROP