What is the CVSS score of CVE-2026-51721?

CVE-2026-51721 has a CVSS 3.1 base score of 9.1 (Critical). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N. EPSS exploitation probability: 0.2%.

Which versions of TOTOLINK T6 are affected by CVE-2026-51721?

The TOTOLINK T6 mesh Wi-Fi router (firmware 4.1.5cu.748_B20211015 and earlier) contains a critical access-control vulnerability (CWE-284) permitting unauthenticated remote attackers to manipulate…

How to fix or mitigate CVE-2026-51721?

Within 24 hours, audit network inventory to identify all TOTOLINK T6 routers running firmware 4.1.5cu.748_B20211015 or earlier and document their network placement. Within 7 days, implement firewall rules blocking external POST requests to the cstecgi.cgi endpoint (specifically the setPairCfg handler); disable mesh networking if operationally feasible; and apply network segmentation to isolate affected routers from administrative networks and sensitive systems. Within 30 days, monitor TOTOLINK security advisories for patches addressing CWE-284 deficiencies and develop a remediation plan including firmware updates or hardware replacement if patching timelines exceed acceptable risk tolerance.

TOTOLINK T6 CVE-2026-51721

EUVD-2026-68674 CRITICAL

Improper Access Control (CWE-284)

2026-08-31 mitre

GHSA-xc9w-qf3x-rv82

Authentication Bypass

9.1

CVSS 3.1 · Vendor: mitre

Severity by source

Vendor (mitre) PRIMARY

9.1 CRITICAL

AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

vuln.today AI

8.2 HIGH

Unauthenticated network POST (AV:N/AC:L/PR:N/UI:N) tampers with mesh pairing config, so I:H; no data disclosure implied (C:N) and pairing disruption gives A:L, not A:N.

3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:L

4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:L/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

None

Lifecycle Timeline

Metadata Corrected

Sep 01, 2026 - 15:40 vuln.today

tag: N A removed

Analysis Generated

Sep 01, 2026 - 15:34 vuln.today

CVSS changed

Sep 01, 2026 - 15:22 NVD

9.1 (CRITICAL)

CVE Published

Aug 31, 2026 - 00:00 cve.org

CRITICAL 9.1

CVE Published

Aug 31, 2026 - 00:00 cve.org

UNKNOWN (no severity yet)

DescriptionCVE.org

Incorrect access control in the setPairCfg function of TOTOLINK T6 4.1.5cu.748_B20211015 allows unauthenticated attackers to alter the mesh pairing state via sending a crafted POST request to /cgi-bin/cstecgi.cgi.

AnalysisAI

Unauthenticated tampering with mesh Wi-Fi pairing on the TOTOLINK T6 router (firmware 4.1.5cu.748_B20211015) lets remote attackers manipulate the device's mesh pairing state by posting to the setPairCfg handler of the cstecgi.cgi endpoint, with no credentials required. The flaw is an access-control gap (CWE-284) reported by MITRE; no public exploit code or active exploitation is currently identified, and EPSS is low (0.16%, 6th percentile), so risk is elevated by the trivial preconditions but not by observed attacker interest.

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

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Vulnerability AssessmentAI

Exploitation	Exploitation requires the attacker to reach the router's HTTP management endpoint /cgi-bin/cstecgi.cgi and send a crafted POST invoking the setPairCfg function; no authentication, user interaction, or non-default setting is needed on the device itself (PR:N/UI:N). … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment	Signals partly agree and partly conflict. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario	Full exploit scenario with step-by-step reproduction available after sign-in.
Remediation	No vendor-released patched firmware version is identified in the available data (no fixed build number is cited), so treat this as 'No vendor-released patch identified at time of analysis' and monitor the TOTOLINK T6 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. … Detailed patch versions, workarounds, and compensating controls in full report.

Recommended ActionAI

Within 24 hours, audit network inventory to identify all TOTOLINK T6 routers running firmware 4.1.5cu.748_B20211015 or earlier and document their network placement. …

Threat intelligence, references, and detailed analysis are available after sign-in.