CVE-2026-51617 Overview
CVE-2026-51617 is an improper access control vulnerability [CWE-284] affecting the TOTOLINK T6 router running firmware version 4.1.5cu.748_B20211015. The flaw resides in the getSysStatusCfg function exposed through the /cgi-bin/cstecgi.cgi endpoint. Unauthenticated remote attackers can send a crafted POST request to retrieve sensitive device and network information without any credentials. Disclosed data includes operation mode, firmware version, serial number, WAN and LAN IP addresses, WiFi SSID, encryption keys, and connected client statistics.
Critical Impact
Unauthenticated attackers can remotely extract WiFi encryption keys and network configuration data from affected TOTOLINK T6 devices over the network.
Affected Products
- TOTOLINK T6 router
- Firmware version 4.1.5cu.748_B20211015
- Devices exposing the /cgi-bin/cstecgi.cgi management interface
Discovery Timeline
- 2026-08-28 - CVE-2026-51617 published to NVD
- 2026-09-01 - Last updated in NVD database
Technical Details for CVE-2026-51617
Vulnerability Analysis
The TOTOLINK T6 exposes a Common Gateway Interface (CGI) handler at /cgi-bin/cstecgi.cgi that dispatches requests to internal functions based on JSON parameters in the POST body. The getSysStatusCfg function returns aggregated system and network configuration data. The function does not verify that the requesting client holds an authenticated session before responding. Any client capable of reaching the device's HTTP management interface can invoke the function and receive the response payload.
The returned data includes credentials of direct security relevance, notably WiFi SSIDs and their encryption keys. Attackers within radio range of the wireless network can use these keys to join the network and pivot to internal systems. Serial numbers and firmware versions also aid in follow-on targeting of additional vulnerabilities specific to the device model and build.
Root Cause
The root cause is a missing authorization check in the getSysStatusCfg request handler. The endpoint treats status queries as low-sensitivity operations and omits session validation. However, the response body embeds high-sensitivity fields such as encryption keys, making the missing check an information disclosure primitive.
Attack Vector
Exploitation requires network reachability to the router's HTTP interface. An attacker sends a crafted POST request to /cgi-bin/cstecgi.cgi invoking the getSysStatusCfg topic. The device responds with the full status structure. When the management interface is exposed to the WAN, exploitation is possible directly from the internet. On LAN-only deployments, any device on the local network, including guest networks or compromised IoT peers, can trigger disclosure.
No verified proof-of-concept code is published. See the GitHub CVE Coordination Resource for coordination details.
Detection Methods for CVE-2026-51617
Indicators of Compromise
- Unauthenticated POST requests to /cgi-bin/cstecgi.cgi containing the getSysStatusCfg topic parameter
- HTTP responses from the router containing WiFi SSID and encryption key fields returned to external or unexpected internal clients
- Repeated CGI polling from a single source IP without a preceding authentication request
Detection Strategies
- Inspect HTTP and HTTPS traffic to router management interfaces for POST requests referencing getSysStatusCfg and correlate with session establishment logs
- Alert on responses from cstecgi.cgi that exceed a baseline size when no authenticated session cookie is present
- Baseline expected administrative source IPs and flag deviations targeting the CGI endpoint
Monitoring Recommendations
- Ingest router and network device logs into a centralized analytics platform for behavioral analysis of management-plane access
- Monitor egress traffic from IoT and network device VLANs for unexpected outbound activity that may follow credential harvesting
- Track WiFi client join events to identify unknown devices connecting after potential key exposure
How to Mitigate CVE-2026-51617
Immediate Actions Required
- Restrict access to the router's HTTP management interface to trusted administrative networks only, and disable WAN-side management
- Segment TOTOLINK T6 devices onto a dedicated management VLAN with firewall rules blocking untrusted clients from reaching /cgi-bin/cstecgi.cgi
- Rotate WiFi pre-shared keys and SSIDs on affected devices, and reissue any credentials that may have been disclosed
Patch Information
No vendor security advisory or firmware patch has been published in the referenced sources at the time of NVD publication. Consult the TOTOLINK Download Page for firmware updates and monitor the TOTOLINK Official Website for advisories. Where a vendor fix is unavailable, replacement with a supported device or strict network isolation is recommended.
Workarounds
- Block inbound TCP traffic to the router's HTTP and HTTPS management ports from the WAN interface at the perimeter firewall
- Deploy access control lists on upstream switches to permit /cgi-bin/cstecgi.cgi access only from designated administrator workstations
- Disable remote management features in the router configuration if not required for operations
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
