CVE-2026-51634 Overview
CVE-2026-51634 is an incorrect access control vulnerability in the getWiFiBasicCfg function of the TOTOLINK T6 router running firmware version 4.1.5cu.748_B20211015. Unauthenticated attackers on the adjacent network can retrieve core wireless configuration data, including Service Set Identifiers (SSIDs) and Wi-Fi keys, by sending a crafted POST request to /cgi-bin/cstecgi.cgi. The weakness is classified under [CWE-284: Improper Access Control].
Critical Impact
Attackers within Wi-Fi range can extract wireless credentials without authentication, enabling network intrusion and downstream lateral movement against connected clients and services.
Affected Products
- TOTOLINK T6 router
- Firmware version 4.1.5cu.748_B20211015
- Web management interface exposing /cgi-bin/cstecgi.cgi
Discovery Timeline
- 2026-08-28 - CVE-2026-51634 published to NVD
- 2026-09-01 - Last updated in NVD database
Technical Details for CVE-2026-51634
Vulnerability Analysis
The TOTOLINK T6 exposes a CGI endpoint at /cgi-bin/cstecgi.cgi that dispatches requests to internal handler functions based on POST body parameters. The getWiFiBasicCfg handler returns the router's wireless configuration, including SSIDs and pre-shared keys. The handler does not validate whether the requester has an authenticated administrative session before returning the data.
An attacker within radio range of the device can therefore issue a single unauthenticated POST request and receive plaintext wireless credentials in the response. This exposes both the primary and any guest or secondary SSIDs configured on the device.
Root Cause
The root cause is missing authorization enforcement on a sensitive read operation. Handlers registered under cstecgi.cgi should reject requests that lack a valid session token for administrative reads. The getWiFiBasicCfg code path omits this check, treating configuration retrieval as an anonymous operation.
Attack Vector
Exploitation requires adjacent network access, meaning the attacker must be associated with the device's wireless network or otherwise reach its LAN interface. No credentials, user interaction, or elevated privileges are required. The attacker sends an HTTP POST request to /cgi-bin/cstecgi.cgi with a body invoking the getWiFiBasicCfg method and parses the JSON response containing SSIDs and Wi-Fi keys.
No verified proof-of-concept code is published in the referenced advisories. See the GitHub CVE Vendor Coordination advisory for coordination details.
Detection Methods for CVE-2026-51634
Indicators of Compromise
- Unauthenticated HTTP POST requests to /cgi-bin/cstecgi.cgi containing the string getWiFiBasicCfg in the request body.
- Access to the router management interface from client MAC addresses that have never authenticated to the admin console.
- Responses from the router web service containing SSID and key fields returned to unauthenticated sessions.
Detection Strategies
- Inspect router access logs, when available, for POST requests to cstecgi.cgi originating from unexpected wireless clients.
- Deploy wireless intrusion detection to flag guest or unauthorized clients probing the gateway's management interface on TCP/80 or TCP/443.
- Correlate new or unknown Wi-Fi client associations followed shortly by rogue access points broadcasting the same SSID and PSK, which would indicate credential reuse by an attacker.
Monitoring Recommendations
- Baseline the set of devices that legitimately reach the router management URL and alert on deviations.
- Monitor for the appearance of duplicate SSIDs in the environment, which may indicate an attacker staging an evil-twin access point.
- Review DHCP and ARP tables regularly for unknown clients that gained network access without an authorized onboarding event.
How to Mitigate CVE-2026-51634
Immediate Actions Required
- Restrict physical and wireless proximity to the affected TOTOLINK T6 devices where feasible, and disable guest networks that share the same management VLAN.
- Block LAN-side access to /cgi-bin/cstecgi.cgi from client subnets using upstream firewall or ACL controls.
- Rotate all SSIDs and Wi-Fi pre-shared keys on affected devices, and assume prior keys are compromised if the device was exposed.
- Monitor the TOTOLINK firmware download page for an updated firmware release addressing the issue.
Patch Information
At the time of NVD publication, no vendor patch is listed in the referenced advisories for firmware 4.1.5cu.748_B20211015. Administrators should consult the TOTOLINK official website and the coordination records at the DarkBoulder and ShengWu00 repositories for updates.
Workarounds
- Segment the router's management interface onto a dedicated administrative VLAN unreachable from client wireless SSIDs.
- Replace affected devices in high-risk environments with hardware that receives active vendor security maintenance.
- Enforce WPA3 or strong WPA2 configurations with unique keys per site so that credential exposure on one device does not cascade to other locations.
# Example: block LAN clients from reaching the router admin CGI (upstream firewall)
iptables -I FORWARD -d 192.168.1.1 -p tcp --dport 80 \
-m string --algo bm --string "/cgi-bin/cstecgi.cgi" -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
