Security readout for executives and security teams
Plain-English summary
A flaw in the specified TOTOLINK T6 firmware allows an unauthenticated network attacker to delete firewall filtering rules. This could weaken the router’s security controls and expose systems or services that those rules protected. The supplied sources do not confirm a vendor fix or attacks in the wild.
Executive priority
Treat affected, remotely manageable devices as an urgent remediation priority. Immediately reduce management-interface exposure and verify firewall integrity. Escalate internet-reachable or externally managed devices first. A confirmed patch is not identified in the supplied evidence, so obtain current vendor guidance before scheduling firmware remediation.
Technical view
CVE-2026-51720 is an incorrect access-control weakness (CWE-284) in delIpPortFilterRules on TOTOLINK T6 firmware 4.1.5cu.748_B20211015. A crafted POST request to /cgi-bin/cstecgi.cgi can remove IP/port firewall rules without authentication. CVSS 3.1 is 9.1: network-accessible, low complexity, no privileges, and no user interaction.
Likely exposure
Confirmed scope is limited to TOTOLINK T6 firmware 4.1.5cu.748_B20211015. Risk is greatest where the management CGI endpoint is reachable from untrusted networks. The bundle provides no CPE inventory or evidence that other models or firmware versions are affected.
Exploitation context
The described request is remotely deliverable and requires neither authentication nor user interaction. However, the bundle marks this CVE as absent from KEV and provides no evidence of active exploitation, public weaponization, or observed attacks. Endpoint reachability remains an important environmental condition.
Researcher notes
The record attributes the flaw to missing access control in delIpPortFilterRules and identifies a specific CGI route and firmware build. CVSS claims high confidentiality and integrity impact, although the description directly establishes firewall-rule deletion. Broader product scope, patch availability, default endpoint exposure, and exploitation telemetry are not established.
Mitigation direction
- Identify TOTOLINK T6 devices running firmware 4.1.5cu.748_B20211015.
- Restrict router management access to trusted administrative networks.
- Disable remote administration from untrusted networks where operationally feasible.
- Check TOTOLINK guidance for corrected firmware or supported mitigation.
- Back up and review firewall rules for unauthorized changes.
Validation and detection
- Verify each device model and installed firmware version.
- Confirm whether /cgi-bin/cstecgi.cgi is reachable from untrusted networks.
- Review current firewall rules against an approved configuration baseline.
- Inspect available logs for unexpected administrative requests or rule deletions.
- Confirm vendor guidance before applying firmware changes.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-284: Authorization and privilege behavior lookup
Authorization weaknesses can support privilege escalation and valid-account review, depending on exploit path. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2026-51720 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Critical
- CVSS
- 9.1 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
SSVC decision data
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N3.95.2CISA-ADPVulnerability scoring details
Base CVSS 3.1 score
9.1CriticalVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- https://www.totolink.net/home/menu/detail/menu_listtpl/download/id/190/ids/36.htmlCVE reference, mitre
- https://www.totolink.net/CVE reference, mitre
- https://github.com/DarkBoulder/CVE-Vendor-Coordination/blob/main/TOTOLINK/README.mdCVE reference, mitre
- https://github.com/ShengWu00/CVE-Vendor-Coordination/blob/main/TOTOLINK/README.mdCVE reference, mitre
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
CWE mapping pending import
This CVE carries a CWE mapping that will resolve to a full Glexia CWE intelligence page after the official CWE import is complete.