CVE-2026-27514: Tenda F3 Information Disclosure Flaw

CVE-2026-27514 Overview

CVE-2026-27514 is a sensitive information exposure vulnerability affecting Shenzhen Tenda F3 Wireless Router firmware V12.01.01.55_multi. The vulnerability exists in the configuration download functionality, where the configuration download response includes the router password and administrative password in plaintext. Additionally, the endpoint omits appropriate Cache-Control directives, which can allow the response to be stored in client-side caches and recovered by other local users or processes with access to cached browser data.

Critical Impact

Attackers with low-privilege network access can retrieve plaintext administrative credentials, enabling complete router compromise and potential network takeover.

Affected Products

• Tenda F3 Firmware V12.01.01.55_multi
• Tenda F3 Wireless Router (Hardware)

Discovery Timeline

• 2026-02-23 - CVE-2026-27514 published to NVD
• 2026-02-23 - Last updated in NVD database

Technical Details for CVE-2026-27514

Vulnerability Analysis

This vulnerability represents a classic sensitive information exposure flaw (CWE-201) in an embedded IoT device. The Tenda F3 router's configuration download feature fails to implement proper security controls, exposing credentials in cleartext within the HTTP response body.

The attack requires only low-privilege authentication to the router's web interface. Once authenticated, an attacker can access the configuration download endpoint and retrieve the complete router configuration, including administrative passwords stored in plaintext format. This design flaw violates fundamental security principles around credential storage and transmission.

The secondary issue compounds the risk: missing Cache-Control headers allow browsers to cache the sensitive response. Even after the original session ends, cached data may persist on disk, enabling credential recovery by other users or malicious processes with filesystem access.

Root Cause

The root cause is twofold: First, the firmware stores and transmits administrative credentials in plaintext rather than using secure hashing or encryption. Second, the HTTP response lacks appropriate Cache-Control directives (such as no-store and no-cache), allowing sensitive data to persist in browser caches. This represents a fundamental design flaw where security was not considered in the configuration export functionality.

Attack Vector

The attack vector is network-based and requires low-privilege authentication to exploit. An attacker with basic access to the router's web interface can navigate to or directly request the configuration download endpoint. The response containing plaintext credentials can be captured through:

1. Direct access to the configuration download functionality with any authenticated session
2. Network traffic interception if HTTPS is not enforced
3. Recovery from browser cache by other local users or malicious processes
4. Cross-site request scenarios if combined with other vulnerabilities

The vulnerability is particularly concerning in shared environments where multiple users access the same workstation, as cached credentials may be recoverable from browser data directories.

Detection Methods for CVE-2026-27514

Indicators of Compromise

• Unusual or unauthorized access to the router configuration download endpoint in web server logs
• Multiple configuration download requests from unexpected source IP addresses
• Evidence of browser cache extraction tools or scripts targeting router configuration data
• Unauthorized administrative login attempts following configuration access patterns

Detection Strategies

• Monitor router access logs for requests to configuration export/download endpoints
• Implement network traffic analysis to detect plaintext credential transmission patterns
• Deploy endpoint detection to identify processes accessing browser cache directories for router-related data
• Configure SIEM rules to correlate configuration download events with subsequent administrative actions

Monitoring Recommendations

• Enable verbose logging on the Tenda F3 router if available and regularly review access logs
• Implement network segmentation to limit access to router management interfaces
• Deploy network monitoring solutions to detect credential exposure in unencrypted traffic
• Conduct periodic audits of browser cache contents on shared workstations for sensitive router data

How to Mitigate CVE-2026-27514

Immediate Actions Required

• Restrict access to the router's web management interface to trusted administrators only
• Implement network segmentation to isolate router management traffic from general network access
• Clear browser caches on any workstation that has accessed the router configuration interface
• Consider replacing affected devices with alternatives that implement proper credential protection

Patch Information

As of the last update on 2026-02-23, no vendor patch has been confirmed for this vulnerability. Organizations should monitor the Tenda F3 Product Page for firmware updates. Additional technical details are available in the VulnCheck Advisory.

Workarounds

• Disable remote management access and restrict web interface access to local wired connections only
• Change administrative credentials regularly and immediately after any configuration download operation
• Implement a firewall or access control list (ACL) to restrict which IP addresses can access the management interface
• Consider deploying a VPN or jump host for administrative access to limit exposure

# Configuration example - Network isolation via iptables (on upstream firewall)
# Block external access to Tenda F3 management interface (assuming router IP 192.168.1.1)
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 only specific management workstation
iptables -I FORWARD -s 192.168.1.100 -d 192.168.1.1 -p tcp --dport 80 -j ACCEPT