EUVD-2026-68591
GHSA-mppv-mgp5-f972
Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain
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AccessReach router web interface (LAN or exposed WAN)
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DeliverySend crafted POST to /cgi-bin/cstecgi.cgi
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ExploitInvoke setPortForwardRules without auth
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ExecutionAdd port-forward rules exposing internal services
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ImpactAccess internal LAN hosts
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 router's HTTP endpoint /cgi-bin/cstecgi.cgi and the ability to send a POST invoking the setPortForwardRules function; no credentials, tokens, or user interaction are needed (CVSS PR:N/UI:N). The key limiting factor is exposure of the management interface: by default the web UI is typically LAN-facing, so internet-wide exploitation depends on the router having remote/WAN management enabled, otherwise an attacker must already be on the local network. Confirmed affected build is TOTOLINK T6 firmware 4.1.5cu.748_B20211015; other firmware versions are unverified from the feed. |
| Impact | The signals conflict in a way defenders should weigh carefully: CVSS 3.1 is 9.8 with AV:N/AC:L/PR:N/UI:N (network, low complexity, no auth, no interaction), which argues for urgent treatment, yet EPSS is only 0.16% (6th percentile) and there is no KEV listing and no identified public exploit - indicating no evidence of widespread automated exploitation today. The realistic exposure hinges on whether the router's management interface (and cstecgi.cgi) is reachable from the WAN; on a default LAN-only deployment the practical attack surface is much smaller than 9.8 implies, whereas any device with remote management exposed is genuinely high risk. The CVSS C:H/I:H/A:H rating is arguably generous for a port-forwarding-exposure primitive whose direct impact is exposing internal services rather than code execution - treat the 9.8 as an upper bound and prioritize based on WAN exposure. Overall: a real, easily-triggered authorization bypass on consumer/SOHO hardware, but current data points to targeted rather than mass exploitation. |
| Exploit ScenarioDerived | An attacker who can reach the router's web interface - for example a device with remote management exposed to the WAN, or an attacker already on the local network - sends a single crafted POST to /cgi-bin/cstecgi.cgi invoking setPortForwardRules without authenticating. This creates forwarding rules that expose internal services (cameras, NAS, admin panels) to the attacker. No public exploit code is identified, but the request is trivial to construct given the low attack complexity. |
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Alert meAnalysisAIv1 – Sep 01, 2026
Access-control bypass in the TOTOLINK T6 router (firmware 4.1.5cu.748_B20211015) lets remote unauthenticated attackers manipulate port-forwarding rules via a crafted POST to /cgi-bin/cstecgi.cgi, exposing internal LAN services to the internet. The setPortForwardRules handler fails to enforce authentication, so anyone able to reach the device's web interface can create NAT/forwarding entries. CVSS is rated 9.8 (critical); no public exploit is identified at time of analysis and EPSS is low (0.16%, 6th percentile), and it is not in CISA KEV.
RemediationAI
No specific vendor-released patched firmware version is identified in the provided data, so treat this as: no vendor-released patch version independently confirmed at time of analysis - check TOTOLINK's download page (https://www.totolink.net/home/menu/detail/menu_listtpl/download/id/190/ids/36.html) for updated T6 firmware superseding 4.1.5cu.748_B20211015 and apply it once available. As compensating controls: disable remote/WAN management on the router so /cgi-bin/cstecgi.cgi is not reachable from the internet (trade-off: loses remote administration); restrict access to the web management interface to trusted LAN hosts or a management VLAN via ACL (trade-off: added network config); and audit and remove any unexpected port-forwarding entries the device is advertising, since this flaw lets attackers add them. Where feasible, place the device behind an upstream firewall that blocks inbound access to its HTTP management port.
Affected VersionsENISA
Affects your stack
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Technical ContextAI · show details
The affected component is the CGI backend (/cgi-bin/cstecgi.cgi) of TOTOLINK's SOHO router firmware, a common single-binary handler that dispatches JSON/form actions by function name - here setPortForwardRules, which programs the device's NAT/port-forwarding table. The root cause is CWE-284 (Improper Access Control): the endpoint does not verify an authenticated/authorized session before mutating configuration. TOTOLINK's cstecgi.cgi has a long history of similar function-level authorization and command-injection flaws across its T6/A-series product lines. The CPE in the feed is a placeholder (cpe:2.3:a:n/a:n/a:*), so the exact affected-product enumeration is not machine-usable and must be taken from the description (T6, firmware 4.1.5cu.748_B20211015).
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Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Unauthenticated network request to cstecgi.cgi (AV:N/AC:L/PR:N/UI:N); primary impact is exposing internal services (C:H), with no demonstrated integrity/availability compromise beyond rule changes, so I set I/A conservatively to N.
Primary rating from Vendor (mitre).
CVSS VectorVendor: mitre
Lifecycle Timeline
3DescriptionCVE.org
Incorrect access control in the setPortForwardRules function of TOTOLINK T6 4.1.5cu.748_B20211015 allows unauthenticated attackers to expose internal services via sending a crafted POST request to /cgi-bin/cstecgi.cgi.
Executive ViewAI
TOTOLINK T6 routers contain an authentication bypass in port-forwarding controls that allows external attackers to redirect internal network services to the internet without credentials. No vendor patch is available. Organizations deploying these devices face immediate exposure of internal LAN services and must implement urgent network-level access controls or execute device replacement.
No vendor-released patch identified at time of analysis. Interim mitigations: (1) Restrict network access to device web interface via firewall ACLs, limiting administrative connections to known-good IP ranges; (2) Implement continuous monitoring and alerting for unauthorized modifications to port-forwarding configuration; (3) Segment router administrative plane from general network traffic if possible; (4) Plan replacement with alternative gateway solutions offering authenticated administrative access controls.
Threat Intelligence Overview
NVD
CVE.org
EPSS
Vulnrichment
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.
What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
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