CVE-2026-7054: Tenda F456 Buffer Overflow Vulnerability

CVE-2026-7054 Overview

A buffer overflow vulnerability has been identified in the Tenda F456 router firmware version 1.0.0.5. This vulnerability affects the fromPptpUserAdd function within the /goform/PPTPDClient endpoint of the httpd component. By manipulating the opttype or usernamewith arguments, an attacker can trigger a buffer overflow condition. The attack can be executed remotely over the network, and exploit details have been made publicly available, increasing the risk of active exploitation.

Critical Impact

Remote attackers with low-level privileges can exploit this buffer overflow to potentially achieve arbitrary code execution on the affected Tenda F456 routers, compromising network security and enabling further lateral movement.

Affected Products

• Tenda F456 Firmware version 1.0.0.5
• Tenda F456 Hardware

Discovery Timeline

• 2026-04-26 - CVE-2026-7054 published to NVD
• 2026-04-29 - Last updated in NVD database

Technical Details for CVE-2026-7054

Vulnerability Analysis

This vulnerability is classified under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer). The fromPptpUserAdd function in the Tenda F456 router's httpd service fails to properly validate the length of user-supplied input in the opttype and usernamewith parameters before copying them into fixed-size memory buffers. When an attacker supplies oversized input values, the function writes beyond the allocated buffer boundaries, corrupting adjacent memory regions.

The vulnerability is exposed through the /goform/PPTPDClient HTTP endpoint, which handles PPTP (Point-to-Point Tunneling Protocol) client configuration. Since this endpoint is accessible over the network and requires only low-level authentication, remote attackers can craft malicious HTTP requests to trigger the overflow condition.

Root Cause

The root cause is improper bounds checking in the fromPptpUserAdd function. The function processes user-supplied parameters (opttype and usernamewith) without validating their length against the destination buffer size. This lack of input validation allows attackers to overflow stack or heap buffers, potentially overwriting return addresses, function pointers, or other critical memory structures.

Attack Vector

The attack is network-based and can be executed remotely. An attacker with low-privilege access to the router's web interface can send a specially crafted HTTP POST request to /goform/PPTPDClient with oversized values for the opttype or usernamewith parameters. This triggers the buffer overflow in the fromPptpUserAdd function, which may lead to denial of service, information disclosure, or arbitrary code execution depending on the memory layout and exploitation technique used.

The vulnerability has been publicly documented, with technical details available in the GitHub Vulnerability Document. The exploit can be executed remotely without user interaction, making it particularly dangerous for internet-facing or inadequately protected router deployments.

Detection Methods for CVE-2026-7054

Indicators of Compromise

• Unusual HTTP POST requests to /goform/PPTPDClient with abnormally long parameter values for opttype or usernamewith
• Router instability, unexpected reboots, or service crashes affecting the httpd process
• Anomalous network traffic patterns originating from or destined to the router's management interface
• Unexpected changes to PPTP client configurations on the device

Detection Strategies

• Deploy network intrusion detection systems (IDS) with signatures that flag HTTP requests to /goform/PPTPDClient containing oversized parameter values
• Monitor router system logs for segmentation faults, memory access violations, or httpd service crashes
• Implement web application firewall (WAF) rules to inspect and limit parameter lengths for requests targeting Tenda router administration endpoints

Monitoring Recommendations

• Enable verbose logging on Tenda F456 routers and forward logs to a centralized SIEM for analysis
• Set up alerting for repeated failed authentication attempts or unusual request patterns to the web management interface
• Regularly audit router configurations for unauthorized changes to PPTP settings

How to Mitigate CVE-2026-7054

Immediate Actions Required

• Restrict network access to the router's web management interface to trusted IP addresses only
• Disable remote management access from the WAN interface if not required
• Place the Tenda F456 router behind a firewall that blocks external access to /goform/ endpoints
• Monitor for firmware updates from Tenda and apply patches immediately when available

Patch Information

As of the last update on 2026-04-29, no official patch from Tenda has been identified in the available CVE data. Administrators should monitor the Tenda Official Site for security advisories and firmware updates addressing this vulnerability. Additional technical details can be found in the VulDB entry #359627.

Workarounds

• Implement access control lists (ACLs) to restrict access to the router's management interface to specific trusted IP addresses
• Use a VPN to secure remote administration sessions rather than exposing the management interface directly
• Consider replacing affected devices with alternative hardware if no patch is released in a timely manner
• Segment the network to isolate the router's management interface from untrusted network segments

# Example: Restrict management access via iptables on upstream firewall
iptables -A FORWARD -d <ROUTER_IP> -p tcp --dport 80 -j DROP
iptables -A FORWARD -s <TRUSTED_ADMIN_IP> -d <ROUTER_IP> -p tcp --dport 80 -j ACCEPT