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TOTOLINK T6 EUVDEUVD-2026-68581

| CVE-2026-51686 CRITICAL
Improper Access Control (CWE-284)
2026-08-31 mitre GHSA-f2f2-48gh-3rvh
9.8
CVSS 3.1 · Vendor: mitre
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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

  1. Access
    Reach router web interface (LAN or exposed WAN)
  2. Delivery
    Craft POST to /cgi-bin/cstecgi.cgi setWiFiEasyCfg
  3. Exploit
    Handler applies config without auth check
  4. Execution
    Rewrite or disable wireless network
  5. Impact
    Wi-Fi outage or weakened security

Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A01:2025 - Broken Access Control
ASVS 5.0
V8 - Authorization Access control enforcement
MITRE ATT&CK

1 technique across 1 tactic: Defense Evasion

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

Exploitation Conditions

Exploitation requires network reachability to the TOTOLINK T6 web management service (default HTTP on /cgi-bin/cstecgi.cgi) and the ability to send a crafted POST invoking the setWiFiEasyCfg function; no credentials, tokens, or user interaction are needed because the handler lacks an access-control check. The primary limiting factor is exposure of the management interface: by default this is LAN-facing, so remote Internet exploitation is only possible where remote/WAN administration is enabled or the interface is otherwise reachable. Affected firmware is specifically T6 4.1.5cu.748_B20211015.

Impact

The provided CVSS 3.1 vector (AV:N/AC:L/PR:N/UI:N, C:H/I:H/A:H = 9.8) treats this as a fully critical network-exploitable flaw, and the network/no-auth/low-complexity portion is consistent with the description. However, the confidentiality impact is overstated: setWiFiEasyCfg is a configuration setter, not a data-read primitive, so realistic impact is integrity (attacker rewrites Wi-Fi config) and availability (attacker disables the wireless network), not high confidentiality - I assess C:N. SSVC aligns with a real-but-not-urgent picture: Exploitation 'none' observed, Automatable 'yes', Technical Impact 'total'. EPSS is low (0.18%), no KEV listing, and no public PoC, so this is a genuine unauthenticated flaw but currently theoretical rather than actively weaponized. Practically, exposure depends on the web interface being reachable - devastating if the admin interface faces the WAN, largely LAN-limited otherwise - and any operator running affected T6 firmware should still prioritize patching given the trivial exploitation path and automatable nature.

Exploit ScenarioDerived

An attacker who can reach the router's web interface - an on-LAN guest, or anyone on the Internet if remote management is enabled - sends a single crafted POST to /cgi-bin/cstecgi.cgi invoking setWiFiEasyCfg with attacker-chosen wireless parameters. Because no authentication is checked, the router applies the change, letting the attacker disable the SSID (denial of service) or weaken/rewrite Wi-Fi security to facilitate further access. No public PoC is currently identified, but the request is trivial to construct given the known endpoint and function name.

Act Now Prioritize within 24-48h. Why: CRITICAL severity.
No patch listed yet 0.2% exploitation probability (EPSS)

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AnalysisAIv1 – Sep 03, 2026

Unauthenticated wireless-network reconfiguration in the TOTOLINK T6 router (firmware 4.1.5cu.748_B20211015) lets remote attackers alter or disable Wi-Fi settings by sending a crafted POST request to the setWiFiEasyCfg handler in /cgi-bin/cstecgi.cgi, which performs no access-control check. Any attacker able to reach the device's web interface can degrade or take down wireless connectivity and weaken Wi-Fi security parameters. No public exploit identified at time of analysis; EPSS is low (0.18%, 7th percentile) and there is no evidence of active exploitation.

RemediationAI

No fixed firmware version is identified in the available data, so no vendor-released patch can be cited at this time - check the TOTOLINK download page (https://www.totolink.net/home/menu/detail/menu_listtpl/download/id/190/ids/36.html) for a firmware release superseding 4.1.5cu.748_B20211015 and apply it once available. As compensating controls, ensure the router's HTTP management interface is not exposed to the WAN/Internet (disable remote administration), which closes remote reachability at the cost of losing off-LAN management; restrict access to /cgi-bin/cstecgi.cgi to trusted management hosts via firewall/ACL where the device supports it; and segment the router's management LAN from untrusted clients so an attacker on the guest/user network cannot reach the CGI endpoint. If the device is end-of-life or unpatched, plan replacement with a supported model, since the setter is unauthenticated by design of the flaw and cannot be authenticated via configuration alone.

Affected VersionsENISA

n/a n/a

Affects your stack

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Technical ContextAI · show details

The TOTOLINK T6 is a consumer/SOHO mesh Wi-Fi router. Like many TOTOLINK devices it exposes a single CGI dispatcher, /cgi-bin/cstecgi.cgi, that routes JSON/form POST requests to internal function handlers by name - here setWiFiEasyCfg, which writes wireless configuration. The root cause is CWE-284 (Improper Access Control): the handler does not verify an authenticated/authorized session before applying configuration changes, so the privileged 'easy config' setter is reachable by anyone who can send a request. This is the write-side counterpart to the many TOTOLINK T6 getters/setters disclosed in the same coordination effort. The supplied CPE (cpe:2.3:a:n/a:n/a:*) is a non-informative NVD placeholder and does not identify the true product; the real affected product is the TOTOLINK T6 router firmware named in the description.

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  • Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

Vendor (mitre) PRIMARY 9.8 CRITICAL
AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
vuln.today AI 9.1 CRITICAL

Unauthenticated network setter with no auth check (AV:N/AC:L/PR:N/UI:N); write-only config gives integrity and availability impact but no data read, so C:N.

3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N

Primary rating from Vendor (mitre).

CVSS VectorVendor: mitre

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

Lifecycle Timeline

3
CVSS changed
Sep 03, 2026 - 18:37 NVD
9.8 (None) 9.8 (CRITICAL)
CVE Published
Aug 31, 2026 - 00:00 cve.org
CRITICAL 9.8
CVE Published
Aug 31, 2026 - 00:00 cve.org
UNKNOWN (no severity yet)

DescriptionCVE.org

Incorrect access control in the setWiFiEasyCfg function of TOTOLINK T6 4.1.5cu.748_B20211015 allows unauthenticated attackers to reconfigure or disable wireless networks via sending a crafted POST request to /cgi-bin/cstecgi.cgi.

Executive ViewAI

Why It Matters

TOTOLINK T6 routers (firmware 4.1.5cu.748_B20211015 and prior) allow remote attackers to arbitrarily reconfigure or disable Wi-Fi networks without authentication; no public exploit identified at time of analysis, but the vulnerability requires no special access and affects all connected users. Organizations relying on these devices should prioritize identifying affected infrastructure and implementing protective controls immediately, as the low EPSS (0.2%) may not reflect emerging attacker interest once detailed technical information spreads.

Business Impact: High
Compensating Controls

No vendor-released patch identified at time of analysis. Interim mitigations include: (1) restrict web-interface access via firewall to administrative networks only; (2) disable UPnP and remote management if enabled; (3) monitor router logs for suspicious POST requests to /cgi-bin/cstecgi.cgi; (4) implement network segmentation to prevent a compromised Wi-Fi configuration from affecting business-critical systems; (5) enforce strong, non-default admin credentials; (6) consider device replacement if no patched firmware is released within 90 days.

Threat Intelligence Overview

EPSS Score
0.2%
Top 93% exploitable
Prevalence
Low
consumer/SOHO TOTOLINK router, niche footprint, single EOL-era firmware
Data Quality
6 sources
Confidence: High
EUVD NVD CVE.org EPSS Vulnrichment GitHub VulDB

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity CRITICAL
CISA KEV No
Public POC No
EPSS 0.2%
Patch available No
Active threat No
Deciding rule
CRITICAL severity
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision
Scheduled
Exploitation
None
System Exposure· derived
Open
Automatable
Yes
Human Impact
High
Technical Impact
Total

Priority Score

49
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +49
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Authentication bypass attacks exploit flaws in the verification mechanisms that control access to systems and applications.

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