CVE-2026-7056 Overview
A buffer overflow vulnerability has been identified in the Tenda F456 router running firmware version 1.0.0.5. The vulnerability exists in the fromSafeUrlFilter function within the /goform/SafeUrlFilter endpoint of the httpd web service. An attacker can exploit this flaw by manipulating the page argument, triggering a buffer overflow condition that could lead to code execution or denial of service on the affected device.
Critical Impact
This remotely exploitable buffer overflow in the Tenda F456 router's web interface can be leveraged by authenticated attackers over the network to potentially execute arbitrary code or crash the device, compromising network security.
Affected Products
- Tenda F456 Firmware version 1.0.0.5
- Tenda F456 Hardware devices
- Tenda F456 routers with vulnerable httpd service
Discovery Timeline
- 2026-04-26 - CVE-2026-7056 published to NVD
- 2026-04-29 - Last updated in NVD database
Technical Details for CVE-2026-7056
Vulnerability Analysis
This vulnerability is classified as CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer). The core issue resides in the fromSafeUrlFilter function, which processes user-supplied input from the page parameter without adequate boundary checks. When processing HTTP requests to /goform/SafeUrlFilter, the vulnerable function copies user-controlled data into a fixed-size buffer without validating the length of the input.
The attack can be performed remotely over the network, requiring only low-privilege authentication to the router's web interface. No user interaction is required to trigger the vulnerability, making it particularly dangerous in scenarios where attackers have gained access to the local network segment.
Root Cause
The root cause of this vulnerability stems from insufficient input validation in the fromSafeUrlFilter function. The function fails to properly validate the length of the page argument before copying it into a stack-allocated buffer. This lack of bounds checking allows an attacker to supply an oversized input that overwrites adjacent memory, potentially including the return address or other critical data structures. This is a classic example of unsafe memory handling common in embedded device firmware written in C.
Attack Vector
The attack vector is network-based, targeting the httpd web service running on the Tenda F456 router. An attacker with low-privilege access to the router's web interface can craft a malicious HTTP request to the /goform/SafeUrlFilter endpoint with an oversized page parameter. The malformed request causes the fromSafeUrlFilter function to overflow the stack buffer, potentially allowing the attacker to:
- Corrupt adjacent memory regions and crash the httpd service (denial of service)
- Overwrite the return address to redirect execution flow
- Execute arbitrary code in the context of the httpd process
The exploitation details are publicly available according to the vulnerability disclosure. For technical analysis, refer to the GitHub Vulnerability Report or the VulDB entry #359629.
Detection Methods for CVE-2026-7056
Indicators of Compromise
- Anomalous HTTP POST requests to /goform/SafeUrlFilter with unusually large page parameter values
- Unexpected crashes or restarts of the httpd service on Tenda F456 devices
- Network traffic patterns showing repeated exploitation attempts against the vulnerable endpoint
- Log entries indicating buffer overflow conditions or segmentation faults in the router's system logs
Detection Strategies
- Monitor network traffic for HTTP requests to /goform/SafeUrlFilter containing abnormally long parameter values
- Implement intrusion detection rules to flag requests exceeding expected parameter lengths to Tenda router endpoints
- Deploy network-based anomaly detection to identify exploitation attempts targeting IoT and router devices
- Use SentinelOne Singularity to detect anomalous behavior patterns indicative of exploitation
Monitoring Recommendations
- Enable logging on all network boundary devices to capture traffic to embedded device management interfaces
- Establish baseline network behavior patterns for router administration traffic
- Configure alerts for repeated failed authentication attempts followed by requests to vulnerable endpoints
- Regularly audit firmware versions across all Tenda devices in your environment
How to Mitigate CVE-2026-7056
Immediate Actions Required
- Restrict access to the router's web management interface to trusted IP addresses only
- Disable remote management capabilities if not explicitly required
- Segment IoT and network infrastructure devices from critical production networks
- Monitor for exploitation attempts while awaiting an official firmware update from Tenda
Patch Information
No official patch information is currently available from Tenda. Organizations should monitor the Tenda Official Website for firmware updates addressing this vulnerability. In the interim, implement the workarounds and network segmentation strategies outlined below to reduce exposure.
Workarounds
- Configure firewall rules to limit access to the /goform/SafeUrlFilter endpoint from untrusted networks
- Place Tenda F456 devices behind a dedicated VLAN with strict access controls
- Disable the web management interface and use alternative management methods if available
- Consider replacing affected devices with alternatives that have a stronger security track record
# Example firewall rule to restrict access to router management interface
# Adjust interface and IP ranges according to your network topology
iptables -A INPUT -p tcp --dport 80 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
