CVE-2026-7099: Tenda F456 Buffer Overflow Vulnerability

CVE-2026-7099 Overview

A buffer overflow vulnerability has been identified in Tenda F456 router firmware version 1.0.0.5. The vulnerability exists in the formQuickIndex function within the /goform/QuickIndex component of the httpd service. An attacker can manipulate the mit_linktype argument to trigger a buffer overflow condition, potentially allowing remote code execution on the affected device.

Critical Impact

Remote attackers can exploit this buffer overflow vulnerability over the network to potentially execute arbitrary code or cause denial of service on vulnerable Tenda F456 routers running firmware version 1.0.0.5.

Affected Products

• Tenda F456 Firmware version 1.0.0.5
• Tenda F456 Hardware Device

Discovery Timeline

• 2026-04-27 - CVE-2026-7099 published to NVD
• 2026-04-30 - Last updated in NVD database

Technical Details for CVE-2026-7099

Vulnerability Analysis

This vulnerability is classified as CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer). The formQuickIndex function in the Tenda F456's embedded web server (httpd) fails to properly validate the length of user-supplied input passed through the mit_linktype parameter. When processing HTTP requests to the /goform/QuickIndex endpoint, the function copies user-controlled data into a fixed-size buffer without adequate bounds checking, leading to a classic buffer overflow condition.

The network-accessible nature of this vulnerability, combined with low attack complexity and no user interaction requirements, makes it particularly dangerous for exposed devices. A public exploit is reportedly available, increasing the risk of exploitation in the wild.

Root Cause

The root cause of this vulnerability is insufficient input validation in the formQuickIndex function. The mit_linktype argument is accepted from HTTP request parameters and processed without proper length verification before being copied into a stack or heap buffer. This lack of boundary checking allows an attacker to supply an overly long string that overwrites adjacent memory, potentially corrupting control flow data such as return addresses or function pointers.

Attack Vector

The attack can be initiated remotely over the network by sending a specially crafted HTTP request to the /goform/QuickIndex endpoint on the vulnerable Tenda F456 router. The attacker must have low-level privileges (authenticated access) to reach the vulnerable function.

The exploitation flow involves:

1. An attacker identifies a Tenda F456 router running firmware version 1.0.0.5
2. The attacker crafts a malicious HTTP request targeting /goform/QuickIndex
3. The request includes an oversized value for the mit_linktype parameter
4. The formQuickIndex function processes the request without proper bounds checking
5. The buffer overflow occurs, potentially allowing code execution or causing a crash

For technical details on the vulnerability mechanism, refer to the GitHub PoC Repository and VulDB entry #359674.

Detection Methods for CVE-2026-7099

Indicators of Compromise

• Unusual HTTP POST requests to /goform/QuickIndex containing abnormally long mit_linktype parameter values
• Unexpected crashes or reboots of the Tenda F456 router's httpd service
• Network traffic anomalies indicating reconnaissance or exploitation attempts against the router's web interface
• Evidence of unauthorized configuration changes or persistent access mechanisms on the device

Detection Strategies

• Monitor network traffic for HTTP requests to /goform/QuickIndex endpoints with unusually large payloads or malformed parameters
• Implement intrusion detection system (IDS) rules to flag requests containing excessively long mit_linktype values
• Configure web application firewall (WAF) rules to inspect and limit parameter lengths for Tenda router management interfaces
• Establish baseline behavior for router web interface traffic and alert on deviations

Monitoring Recommendations

• Enable logging on network security devices to capture all traffic to and from Tenda router management interfaces
• Deploy network-based anomaly detection to identify exploitation attempts targeting embedded device web servers
• Regularly review router access logs for suspicious authentication patterns or unusual API calls
• Monitor for unexpected outbound connections from the router that may indicate compromise

How to Mitigate CVE-2026-7099

Immediate Actions Required

• Restrict access to the router's web management interface to trusted internal networks only
• Disable remote management features if not required for operations
• Implement network segmentation to isolate vulnerable devices from untrusted network segments
• Deploy firewall rules to block external access to port 80/443 on the Tenda F456 device

Patch Information

At the time of publication, no official patch from Tenda has been referenced in the available vulnerability data. Organizations should monitor the Tenda Official Website for firmware updates addressing this vulnerability. Contact Tenda support directly for information on remediation options.

For additional vulnerability intelligence, refer to:

• VulDB Entry #359674
• VulDB CTI Information

Workarounds

• Place the Tenda F456 router behind an additional firewall that filters access to the /goform/ directory
• Implement IP whitelisting to restrict web interface access to specific management workstations
• Consider replacing the vulnerable device with an alternative router if no patch becomes available
• Use VPN access for any remote management requirements instead of exposing the web interface directly

# Example iptables rules to restrict access to Tenda router web interface
# Apply on an upstream firewall or gateway device

# Block external access to router management interface (adjust IP as needed)
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 80 -j DROP
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 443 -j DROP

# Allow access only from trusted management subnet
iptables -I FORWARD -s 192.168.10.0/24 -d 192.168.1.1 -p tcp --dport 80 -j ACCEPT