CVE-2018-25317: Tenda Router Auth Bypass Vulnerability

CVE-2018-25317 Overview

CVE-2018-25317 is a critical authentication bypass vulnerability affecting Tenda W3002R, A302, and W309R wireless routers running firmware version V5.07.64_en. The vulnerability stems from a cookie session weakness that allows unauthenticated attackers to modify DNS settings without proper authentication. By exploiting insufficient session validation, attackers can send malicious GET requests to the /goform/AdvSetDns endpoint with a crafted admin language cookie to change primary and secondary DNS servers, effectively redirecting all user traffic to malicious DNS servers.

Critical Impact

Unauthenticated attackers can hijack DNS configurations on vulnerable Tenda routers, enabling man-in-the-middle attacks, traffic interception, and redirection of users to malicious websites without any user interaction.

Affected Products

• Tenda W3002R wireless router firmware version V5.07.64_en
• Tenda A302 wireless router firmware version V5.07.64_en
• Tenda W309R wireless router firmware version V5.07.64_en

Discovery Timeline

• 2026-04-29 - CVE-2018-25317 published to NVD
• 2026-04-29 - Last updated in NVD database

Technical Details for CVE-2018-25317

Vulnerability Analysis

This vulnerability is classified under CWE-290 (Authentication Bypass by Spoofing), which involves circumventing authentication mechanisms by manipulating or forging authentication credentials. The root issue lies in how the Tenda router firmware handles session validation for administrative functions.

The vulnerable endpoint /goform/AdvSetDns accepts DNS configuration changes without properly validating the authenticity of the session. Instead of implementing robust session management with cryptographically secure tokens, the firmware relies on a flawed cookie-based mechanism that can be easily spoofed. An attacker can craft a request with a manipulated admin language cookie that the router incorrectly interprets as an authenticated administrative session.

The network-accessible nature of this vulnerability means that any attacker who can reach the router's web interface—whether from the local network or, in misconfigured scenarios, from the internet—can exploit this flaw without requiring any credentials.

Root Cause

The root cause is insufficient session validation in the Tenda router firmware's web interface. The /goform/AdvSetDns endpoint fails to properly verify that incoming requests originate from an authenticated administrative session. The firmware appears to use a weak cookie-based authentication mechanism where the presence of a specific cookie value (the admin language cookie) is incorrectly treated as proof of authentication. This design flaw allows attackers to bypass authentication entirely by simply including the expected cookie in their requests.

Attack Vector

The attack is network-based and requires no authentication or user interaction. An attacker can exploit this vulnerability through the following method:

1. The attacker identifies a vulnerable Tenda router (W3002R, A302, or W309R) running firmware V5.07.64_en accessible on the network
2. The attacker crafts an HTTP GET request to the /goform/AdvSetDns endpoint
3. The request includes a spoofed admin language cookie that bypasses session validation
4. The request parameters specify malicious primary and secondary DNS server addresses
5. The router accepts the configuration change, redirecting all DNS queries to attacker-controlled servers

Once DNS settings are modified, all devices using the router for DNS resolution will have their traffic subject to manipulation. Attackers can redirect users to phishing sites, intercept credentials, inject malicious content, or block access to legitimate services. For additional technical details, refer to the Exploit-DB #44380 and the VulnCheck Advisory on Tenda.

Detection Methods for CVE-2018-25317

Indicators of Compromise

• Unexpected changes to DNS server settings on Tenda routers (primary or secondary DNS pointing to unfamiliar IP addresses)
• HTTP GET requests to /goform/AdvSetDns in router access logs without corresponding authenticated admin sessions
• User complaints about websites redirecting to unexpected destinations or SSL/TLS certificate warnings
• DNS queries from network devices being resolved by non-configured DNS servers

Detection Strategies

• Monitor network traffic for HTTP requests to /goform/AdvSetDns on Tenda router management interfaces
• Implement network segmentation to detect unauthorized access attempts to router administration endpoints
• Deploy intrusion detection systems (IDS) with rules targeting DNS hijacking attack patterns against Tenda devices
• Regularly audit router DNS configurations and compare against known-good baselines

Monitoring Recommendations

• Enable and review access logs on Tenda routers to identify suspicious administrative requests
• Implement alerting for any DNS configuration changes on network devices
• Monitor for unusual DNS traffic patterns that may indicate redirection to malicious servers
• Deploy SentinelOne Singularity platform to detect and respond to indicators of DNS-based attacks across endpoints

How to Mitigate CVE-2018-25317

Immediate Actions Required

• Restrict access to the router's web management interface to trusted internal networks only
• Disable remote management features if enabled
• Place vulnerable routers behind a firewall that blocks external access to management interfaces
• Verify and document current DNS settings, then monitor for unauthorized changes
• Consider replacing vulnerable Tenda routers with devices from vendors that provide security updates

Patch Information

No official patch has been identified from Tenda for this vulnerability. The affected firmware version V5.07.64_en appears to be end-of-life with no security updates available. Organizations should contact Tenda support for any available firmware updates or consider replacing vulnerable devices with supported alternatives.

Workarounds

• Implement network access control lists (ACLs) to restrict access to the router management interface (typically port 80/443) to specific trusted IP addresses
• Deploy a firewall rule blocking external access to /goform/* endpoints on Tenda router IP addresses
• Use a separate VLAN for router management traffic, isolated from general user traffic
• Configure downstream devices to use hardcoded DNS servers rather than relying on DHCP-assigned router DNS
• Schedule regular audits of router configurations to detect unauthorized DNS changes

# Example iptables rule to restrict access to router management (adjust IP addresses as needed)
# Block external access to router management on port 80
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 80 -j DROP

# Allow only trusted admin workstation to access router
iptables -I FORWARD -s 192.168.1.100 -d 192.168.1.1 -p tcp --dport 80 -j ACCEPT