CVE-2026-5526: Tenda 4g03 Pro Auth Bypass Vulnerability

CVE-2026-5526 Overview

CVE-2026-5526 is an improper access control vulnerability [CWE-266] affecting the Tenda 4G03 Pro router. The flaw resides in unknown functionality within the /bin/httpd binary that handles the device's web management interface. Attackers can exploit the weakness remotely over the network without authentication or user interaction. Public disclosure indicates exploit details have been released, increasing the risk of opportunistic attacks against exposed devices. The vulnerability impacts firmware version 04.03.01.53 and hardware revisions 1.0 and 1.1, with the default management interface at 192.168.0.1.

Critical Impact
Remote, unauthenticated attackers can abuse improper access controls in the /bin/httpd service to interact with restricted functionality on affected Tenda 4G03 Pro routers.

Affected Products

Tenda 4G03 Pro hardware revision 1.0
Tenda 4G03 Pro hardware revision 1.1
Tenda 4G03 Pro firmware 04.03.01.53

Discovery Timeline

2026-04-04 - CVE-2026-5526 published to NVD
2026-04-30 - Last updated in NVD database

Technical Details for CVE-2026-5526

Vulnerability Analysis

The vulnerability resides in the /bin/httpd web server binary that powers the management interface on Tenda 4G03 Pro routers. The component fails to enforce proper access controls on a specific endpoint or handler. Remote attackers can reach the vulnerable functionality across the network without supplying credentials. Successful exploitation produces limited impact on confidentiality, integrity, and availability of the device. Because the router's httpd typically runs with elevated privileges on embedded Linux, unauthorized access to restricted features can affect device behavior and exposed configuration data.

Root Cause

The root cause is classified under [CWE-266] Incorrect Privilege Assignment. The httpd binary assigns or honors privileges that should be reserved for authenticated administrators. Specific code paths do not validate the caller's authorization context before executing privileged logic. Because the request handling logic trusts unauthenticated inputs at the network boundary, attackers can invoke restricted operations directly.

Attack Vector

The attack vector is network-based and requires no authentication or user interaction. An attacker sends crafted HTTP requests to the router's management interface, typically reachable at 192.168.0.1 on the LAN or via any interface that exposes the web service. Devices with WAN-side management enabled are reachable from the internet, expanding the attack surface. The exploit has been released publicly according to the vendor advisory references, which lowers the skill barrier for opportunistic abuse.

No verified proof-of-concept code is available in trusted public repositories for republishing. Refer to the VulDB Vulnerability #355279 entry and the VulDB CTI for #355279 for technical breakdown details.

Detection Methods for CVE-2026-5526

Indicators of Compromise

Unexpected HTTP requests to the router's management interface (192.168.0.1 or assigned management IP) from untrusted sources or unusual internal hosts.
Configuration changes on the Tenda 4G03 Pro that do not correspond to documented administrator activity.
Connections to /bin/httpd-served endpoints originating from WAN-side IP addresses when remote management is presumed disabled.

Detection Strategies

Inspect router logs and upstream firewall logs for HTTP/HTTPS requests targeting the management interface from non-administrative source addresses.
Use network traffic analysis to identify anomalous request patterns or parameters directed at httpd endpoints on Tenda devices.
Cross-reference firmware version 04.03.01.53 against asset inventories to identify exposed devices requiring monitoring.

Monitoring Recommendations

Enable persistent logging on the router and forward syslog to a centralized collector for retention and search.
Alert on any inbound traffic to TCP port 80/443 of router WAN interfaces from external sources.
Track configuration drift on affected devices using scheduled snapshots of routing, DNS, and credential settings.

How to Mitigate CVE-2026-5526

Immediate Actions Required

Disable remote (WAN-side) management on the Tenda 4G03 Pro until a vendor patch is verified and applied.
Restrict access to the router's management interface to a dedicated administrative VLAN or trusted host list.
Rotate administrator credentials and review configuration for unauthorized modifications.
Monitor the Tenda Company Website for firmware updates addressing CVE-2026-5526.

Patch Information

At the time of publication, no vendor advisory or patched firmware release is referenced in the NVD entry. Customers should track the Tenda Company Website and the VulDB Vulnerability #355279 record for updates. Apply firmware updates that supersede version 04.03.01.53 once the vendor publishes a fix that explicitly addresses improper access control in /bin/httpd.

Workarounds

Place the router behind an upstream firewall and block inbound connections to the management interface from untrusted networks.
Disable any port-forwarding rules that expose the device's web administration interface to the internet.
Segment IoT and management networks so that only authorized administrators can reach 192.168.0.1 or the device's assigned management address.

bash

# Example: block external access to the router management interface upstream
# Replace <ROUTER_IP> with the Tenda 4G03 Pro management address
iptables -I FORWARD -d <ROUTER_IP> -p tcp --dport 80 -j DROP
iptables -I FORWARD -d <ROUTER_IP> -p tcp --dport 443 -j DROP