CVE-2026-7080: Tenda F456 Buffer Overflow Vulnerability

CVE-2026-7080 Overview

A buffer overflow vulnerability has been identified in Tenda F456 routers running firmware version 1.0.0.5. This security flaw affects the fromPPTPUserSetting function within the /goform/PPTPUserSetting endpoint of the httpd component. An attacker can exploit this vulnerability by manipulating the delno argument, causing a buffer overflow condition that may lead to denial of service or arbitrary code execution. The vulnerability can be exploited remotely over the network, and a proof-of-concept exploit has been publicly disclosed.

Critical Impact

This buffer overflow vulnerability in the Tenda F456 router's web interface allows remote authenticated attackers to potentially execute arbitrary code or cause system instability by sending specially crafted requests to the PPTP user settings endpoint.

Affected Products

• Tenda F456 Firmware version 1.0.0.5
• Tenda F456 hardware devices running vulnerable firmware

Discovery Timeline

• 2026-04-27 - CVE-2026-7080 published to NVD
• 2026-04-30 - Last updated in NVD database

Technical Details for CVE-2026-7080

Vulnerability Analysis

This vulnerability is classified as CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer), indicating that the affected function fails to properly validate input boundaries before performing memory operations. The fromPPTPUserSetting function in the httpd service does not adequately sanitize user-supplied input passed through the delno parameter, allowing an attacker to overflow buffer boundaries.

The affected component is exposed via the device's web administration interface, making it accessible to any user with network access to the router's management portal. While the attack requires low-privilege authentication, successful exploitation could allow an attacker to overwrite adjacent memory, potentially corrupting program control structures or injecting malicious code.

Root Cause

The root cause of this vulnerability lies in improper bounds checking within the fromPPTPUserSetting function. When processing the delno argument from HTTP POST requests to /goform/PPTPUserSetting, the function copies user-supplied data into a fixed-size buffer without validating the input length. This classic buffer overflow pattern allows attackers to write beyond allocated memory boundaries.

Attack Vector

The attack is network-based and can be initiated remotely. An authenticated attacker sends a specially crafted HTTP request to the /goform/PPTPUserSetting endpoint with an oversized or malformed delno parameter. The httpd service processes this request without proper input validation, triggering the buffer overflow condition.

The vulnerability exploits the PPTP (Point-to-Point Tunneling Protocol) user configuration functionality, which is commonly used for VPN settings on consumer routers. The attacker does not require physical access to the device, only network connectivity to the router's management interface.

Technical details and proof-of-concept information are available in the GitHub PoC Repository and VulDB #359655.

Detection Methods for CVE-2026-7080

Indicators of Compromise

• Unexpected crashes or reboots of the Tenda F456 router's httpd service
• Anomalous HTTP POST requests targeting /goform/PPTPUserSetting with unusually large delno parameter values
• Memory corruption errors or segmentation faults in router logs
• Unauthorized configuration changes to PPTP VPN settings

Detection Strategies

• Monitor HTTP traffic to router management interfaces for requests to /goform/PPTPUserSetting with oversized parameters
• Implement intrusion detection signatures that flag buffer overflow patterns in web requests targeting Tenda router endpoints
• Deploy network-based anomaly detection to identify unusual traffic patterns to router administration ports
• Review router logs for httpd service instability or unexpected restarts

Monitoring Recommendations

• Enable logging on the Tenda F456 router if available and monitor for service crashes
• Segment router management interfaces from untrusted networks using VLANs or firewall rules
• Implement network monitoring to detect exploitation attempts against IoT and router devices
• Consider deploying a web application firewall (WAF) in front of router management interfaces where feasible

How to Mitigate CVE-2026-7080

Immediate Actions Required

• Restrict access to the router's web administration interface to trusted IP addresses only
• Disable remote management access from WAN interfaces if not required
• Place the router's management interface behind a firewall or on an isolated management network
• Monitor Tenda's official channels for firmware updates addressing this vulnerability

Patch Information

As of the last modification date (2026-04-30), no official patch has been published by Tenda for this vulnerability. Administrators should monitor the Tenda Official Site for security updates and firmware releases. Organizations should implement the workarounds below until a patch becomes available.

Workarounds

• Disable the PPTP user configuration feature if not actively in use
• Implement access control lists (ACLs) to restrict which IP addresses can access the router's management interface
• Use strong authentication credentials and ensure default passwords have been changed
• Consider replacing vulnerable devices with alternative hardware if a patch is not released in a timely manner

# Example: Restrict management access via iptables (on upstream firewall)
# Block external access to router management port
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 management access only from trusted admin workstation
iptables -I FORWARD -s 192.168.1.100 -d 192.168.1.1 -p tcp --dport 80 -j ACCEPT