CVE-2026-27513: Tenda F3 Firmware CSRF Vulnerability

CVE-2026-27513 Overview

Shenzhen Tenda F3 Wireless Router firmware V12.01.01.55_multi contains a cross-site request forgery (CSRF) vulnerability in the web-based administrative interface. The interface does not implement anti-CSRF protections, allowing an attacker to induce an authenticated administrator to submit state-changing requests, which can result in unauthorized configuration changes.

Critical Impact

An attacker can trick authenticated administrators into unknowingly executing malicious actions, potentially compromising router configuration, network security settings, and device access controls.

Affected Products

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

Discovery Timeline

• 2026-02-23 - CVE CVE-2026-27513 published to NVD
• 2026-02-23 - Last updated in NVD database

Technical Details for CVE-2026-27513

Vulnerability Analysis

This vulnerability stems from the absence of Cross-Site Request Forgery (CSRF) protections in the Tenda F3 router's web-based management interface. CSRF attacks exploit the trust that a web application has in authenticated user sessions. When an administrator is logged into the router's management console, their browser maintains an active session with valid authentication credentials.

An attacker can craft a malicious web page containing hidden forms or JavaScript that automatically submits requests to the router's management interface. When an authenticated administrator visits the attacker's page (via phishing, malicious advertisements, or compromised websites), their browser automatically includes the session credentials with the forged requests, causing the router to accept them as legitimate administrative actions.

The vulnerability allows attackers to perform any administrative action the victim is authorized to execute, including modifying DNS settings, changing wireless configurations, creating administrative accounts, or disabling security features—all without the administrator's knowledge or consent.

Root Cause

The root cause of CVE-2026-27513 is the failure to implement anti-CSRF tokens or other request validation mechanisms in the web-based administrative interface. The router's web application accepts state-changing requests based solely on session authentication without verifying that the request originated from a legitimate user interaction within the management interface. This design flaw violates security best practices that require secondary verification mechanisms such as cryptographic tokens, referer header validation, or SameSite cookie attributes to prevent forged cross-origin requests.

Attack Vector

The attack is network-based and requires user interaction from an authenticated administrator. An attacker must first craft a malicious payload targeting specific router management endpoints and then trick an administrator into loading the malicious content while they have an active authenticated session with the router. The attack can be delivered through various vectors:

A typical exploitation scenario involves the attacker hosting a webpage containing hidden HTML forms with pre-filled values targeting the router's configuration endpoints. When the victim visits this page, JavaScript automatically submits the forms, sending forged requests to the router. Common attack payloads include changing the administrative password, modifying DNS server settings to enable DNS hijacking, altering wireless security settings, or enabling remote management features.

The attacker does not need direct network access to the target router—they only need to lure the administrator to a controlled webpage while the administrator maintains an active session. For additional technical details, see the VulnCheck Security Advisory.

Detection Methods for CVE-2026-27513

Indicators of Compromise

• Unexpected changes to router configuration settings, including DNS servers, wireless passwords, or administrative credentials
• New administrative user accounts appearing without authorized creation
• Remote management features enabled when they should be disabled
• Unusual outbound connections or DNS resolution patterns indicating potential DNS hijacking

Detection Strategies

• Monitor router configuration audit logs for unexpected state changes, particularly those occurring in rapid succession or at unusual times
• Implement network monitoring to detect access to known CSRF payload hosting sites or suspicious cross-origin requests targeting router management interfaces
• Deploy browser-based security extensions that warn users about potential CSRF attacks or block automatic form submissions to internal network addresses
• Compare current router configuration snapshots against known-good baselines to identify unauthorized modifications

Monitoring Recommendations

• Enable and regularly review administrative access logs on the Tenda F3 router
• Configure network-level monitoring to alert on configuration change events from router management interfaces
• Implement DNS monitoring to detect unexpected changes in DNS resolution that could indicate successful CSRF exploitation
• Establish a regular schedule for reviewing router configurations against documented security baselines

How to Mitigate CVE-2026-27513

Immediate Actions Required

• Always log out of the router management interface after completing administrative tasks to minimize session exposure
• Use a dedicated browser profile or browser instance exclusively for router administration to prevent cross-site attacks
• Avoid clicking on unknown links or browsing untrusted websites while logged into the router management interface
• Consider implementing network segmentation to limit access to the router's management interface from trusted devices only

Patch Information

As of the last NVD update on 2026-02-23, no official patch has been released by Tenda for this vulnerability. Administrators should monitor the Tenda Product Page for firmware updates that address this CSRF vulnerability. Until a patch is available, implement the workarounds and mitigations described below to reduce risk exposure.

Workarounds

• Restrict access to the router's web management interface to specific trusted IP addresses or MAC addresses using access control lists
• Disable remote management features to limit attack surface to the local network
• Configure browser settings to block third-party cookies and restrict cross-origin requests to internal network addresses
• Consider using network firewalls or access control mechanisms to prevent untrusted devices from reaching the router's management interface

# Network-level access restriction example (external firewall)
# Block external access to router management port
iptables -A FORWARD -p tcp --dport 80 -d 192.168.0.1 -j DROP
iptables -A FORWARD -p tcp --dport 443 -d 192.168.0.1 -j DROP
# Allow management access only from specific trusted workstation
iptables -A FORWARD -p tcp --dport 80 -s 192.168.0.100 -d 192.168.0.1 -j ACCEPT