CVE-2026-11524: Tenda W20E Stack Overflow in WiFi Filter Management – CVSS 8.8

Technical summary

CVE-2026-11524 is a stack-based buffer overflow in the /goform/modifyWifiFilterRules endpoint of Tenda W20E 15.11.0.6's web management interface. The vulnerability stems from insufficient bounds checking on the wifiFilterListRemark parameter, which is processed by the modifyWifiFilterRules function without adequate size validation before being written to stack memory. This violates CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer) and CWE-121 (Stack-based Buffer Overflow). The attack vector is network-based with low complexity; it requires low-privilege authentication but no user interaction. Exploitation could lead to memory corruption, information disclosure, and arbitrary code execution within the device's web server process context.

Business impact

A successful exploit grants an authenticated attacker code execution on the Tenda router, effectively compromising network perimeter security. This enables lateral movement into the internal network, traffic interception, DNS manipulation, or persistent backdoor installation. For organizations relying on Tenda W20E devices for branch office, campus, or remote site connectivity, this represents a critical control plane compromise. The attack surface expands if any management accounts are weak, shared, or exposed through phishing. Given the public disclosure status, exploit availability increases the operational risk window significantly.

Affected systems

Tenda W20E running firmware version 15.11.0.6 and potentially earlier versions are confirmed affected. The vulnerability is in the web management interface accessible on the default HTTP/HTTPS ports (typically 80/443). Any Tenda W20E device exposed to untrusted networks or operated by users with weak credential hygiene is at direct risk. Verify your device's firmware version via the web interface or CLI to determine exposure.

Exploitability

The vulnerability has been publicly disclosed, and exploit code or proof-of-concept details are known to be in circulation. This significantly accelerates the timeline to active weaponization. Exploitation requires authentication (low-privilege), making it most practical for attackers who have already gained initial access or compromised a management account. However, the barrier to acquiring valid credentials is moderate if default credentials remain unchanged or if password policies are weak. Network-based attack vector with low complexity means any attacker with network access to the management interface can attempt exploitation.

Remediation

Immediate actions: (1) Check Tenda's support website for an updated firmware release addressing CVE-2026-11524 and deploy it to all affected W20E devices. Verify the patch version against the vendor advisory before deployment. (2) Restrict web management interface access via firewall rules—limit access to trusted administrative IP ranges or management VLANs only. (3) Enforce strong, unique credentials for all device management accounts and disable any default or shared passwords. (4) Monitor for suspicious login attempts and management interface activity. Long-term: maintain a firmware update schedule and subscribe to Tenda security advisories.

Patch guidance

Contact Tenda support or consult their security advisory for the patched firmware version. Test any firmware update in a non-production environment first to validate compatibility and functionality. Document the pre-patch and post-patch firmware versions in your change management system. Prioritize patching devices in high-risk network segments (DMZ, site-to-site VPN concentrators) ahead of lower-risk deployments.

Detection guidance

Monitor web server logs on the Tenda device for POST requests to /goform/modifyWifiFilterRules with unusually large or malformed wifiFilterListRemark parameter values. Network-level detection can identify requests with abnormally long parameter payloads via deep packet inspection or WAF rules. Monitor the device's CPU and memory consumption for spikes following management interface activity. If available, enable detailed logging on the web management interface and correlate login events with suspicious requests. Intrusion detection systems should flag requests with payloads exceeding typical WiFi filter remark sizes (verify expected limits in device documentation).

Why prioritize this

This vulnerability merits immediate prioritization due to: (1) HIGH CVSS score (8.8) reflecting complete compromise potential, (2) authenticated but low-friction attack vector—credentials are the only barrier, (3) public disclosure and presumed exploit availability accelerating real-world attack likelihood, (4) impact on critical network infrastructure (perimeter router), and (5) low attack complexity. It should be treated as a 1–2 week remediation target for all exposed W20E devices.

Risk score, explained

The CVSS 3.1 score of 8.8 reflects the combination of network accessibility (AV:N), low attack complexity (AC:L), low privilege requirement (PR:L), and severe impact across confidentiality, integrity, and availability (C:H, I:H, A:H). The score does not account for public disclosure or active exploitation, which further elevates operational risk. The authenticated requirement prevents remote unauthenticated attacks but does not significantly mitigate risk in environments where management credentials are weak or shared.

Frequently asked questions