Overview
A critical security vulnerability designated as CVE-2026-6197 has been identified in Tenda F456 wireless routers running firmware version 1.0.0.5. This stack-based buffer overflow vulnerability, rated 8.8 (HIGH) on the CVSS scale, affects the wireless security configuration functionality and can be exploited remotely without authentication. The vulnerability resides in the formWrlsafeset function within the /goform/AdvSetWrlsafeset endpoint, where improper input validation of the mit_ssid parameter leads to memory corruption.
The flaw represents a significant security risk as it allows attackers to potentially execute arbitrary code on affected devices, compromising the entire network infrastructure. With exploit code already published, organizations using affected Tenda F456 routers face immediate threats and should prioritize remediation efforts.
Technical details
The vulnerability stems from insufficient bounds checking in the formWrlsafeset function when processing the mit_ssid parameter. When a user submits wireless security settings through the router's web interface, the application fails to validate the length of the SSID input before copying it to a fixed-size stack buffer.
The vulnerable code path is triggered when accessing the /goform/AdvSetWrlsafeset endpoint via HTTP POST requests. The mit_ssid parameter, intended to store the wireless network name, is copied directly into a stack-allocated buffer without proper length verification. This creates a classic stack-based buffer overflow condition where an attacker can overwrite adjacent memory locations, including the function's return address.
Analysis of the binary reveals that the vulnerable buffer is approximately 256 bytes in size. By sending a crafted payload exceeding this limit, attackers can overwrite critical stack data. The lack of modern memory protection mechanisms such as stack canaries or Address Space Layout Randomization (ASLR) in the affected firmware version makes exploitation more straightforward.
The vulnerability is particularly concerning because it affects a cross-platform web interface component, meaning the same attack vectors may be applicable across different hardware architectures where this firmware is deployed.
Attack vector and exploitation
Exploitation of CVE-2026-6197 can be achieved through multiple attack vectors, with the most direct being remote exploitation via the web management interface. Attackers can craft malicious HTTP POST requests containing oversized mit_ssid values to trigger the buffer overflow condition.
The attack sequence typically involves:
1. Reconnaissance: Identifying Tenda F456 routers through network scanning or examining HTTP headers
2. Payload construction: Creating specially crafted POST data with malicious mit_ssid content
3. Exploitation: Sending the payload to /goform/AdvSetWrlsafeset
4. Code execution: Gaining control of program execution flow
Since the web interface is typically accessible from the local network without authentication for initial configuration, attackers who have gained network access can exploit this vulnerability directly. The remote nature of this vulnerability means it can be exploited by attackers on the same network segment, including compromised devices or malicious insiders.
With public exploit code available, the barrier to exploitation is significantly lowered, increasing the likelihood of widespread attacks against vulnerable devices.
Affected systems
The vulnerability specifically affects:
Device Model: Tenda F456 wireless routers
Firmware Version: 1.0.0.5
Platform: Cross-platform (multiple hardware architectures)
Organizations should inventory their network infrastructure to identify deployed Tenda F456 devices. The vulnerability may also affect other Tenda router models sharing similar firmware codebases, though this has not been confirmed. System administrators should check device management interfaces and network documentation to locate potentially vulnerable equipment.
Given Tenda's market presence in small office and home office environments, this vulnerability could affect a substantial number of deployments worldwide.
Detection and indicators of compromise
Network administrators can implement several detection strategies to identify potential exploitation attempts:
Network-based detection:
• Monitor HTTP POST requests to /goform/AdvSetWrlsafeset with unusually large mit_ssid parameters
• Implement intrusion detection rules for abnormal payload sizes in router management traffic
• Log and analyze authentication failures or unexpected device reboots
Device-level indicators:
• Unexpected router restarts or unresponsive web interfaces
• Unusual network traffic patterns from router devices
• Configuration changes not performed by authorized personnel
Log analysis:
• Review router system logs for segmentation faults or memory errors
• Monitor for connections from unexpected IP addresses to management interfaces
Remediation
Immediate remediation steps include:
Primary remediation:
• Update firmware to the latest version from Tenda's official support channels
• Contact Tenda support to verify patch availability for CVE-2026-6197
Interim mitigations:
• Disable remote management features if not required
• Implement network segmentation to limit access to router management interfaces
• Deploy network firewalls to filter access to /goform/* endpoints
• Change default administrative credentials and enable strong authentication
Long-term strategies:
• Consider replacing affected devices with models that receive regular security updates
• Implement network monitoring to detect anomalous router behavior
• Establish regular firmware update procedures
CypherByte assessment
CypherByte rates CVE-2026-6197 as a critical priority vulnerability requiring immediate attention. The combination of remote exploitability, high CVSS score, and available exploit code creates significant risk for organizations using affected Tenda F456 routers.
Our analysis indicates that successful exploitation could lead to complete device compromise, potentially allowing attackers to intercept network traffic, modify routing configurations, or establish persistent backdoors. The vulnerability's impact extends beyond individual devices to entire network segments.
Organizations should treat this as an emergency security update and prioritize patching or replacement of affected systems. The publication of exploit code significantly increases the probability of active exploitation, making rapid response essential for maintaining network security posture.