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Zbtlink Routers CVE-2026-74233

| EUVDEUVD-2026-67000 CRITICAL
Use of Hard-coded Cryptographic Key (CWE-321)
2026-08-27 VulnCheck GHSA-2h7p-q23r-5gcf
Command Injection We1326 We2426 C We357 We5926 We5926 Ec Qp We5926 Wd We826 Q We826 T2 We826 Wd Wf3526 P Wg108 Wg3526 Ctn720 W1 Lf 1541 Mt7620N Wrc1
9.3
CVSS 4.0 · Vendor: VulnCheck
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Severity by source

Vendor (VulnCheck) PRIMARY
9.3 CRITICAL
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
vuln.today AI
9.8 CRITICAL

Single unauthenticated UDP packet yields root command execution remotely, so AV:N/AC:L/PR:N/UI:N with full C/I/A; scope unchanged as impact stays on the device.

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

Primary rating from Vendor (VulnCheck).

CVSS VectorVendor: VulnCheck

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
X

Lifecycle Timeline

2
Analysis Generated
Aug 27, 2026 - 13:33 vuln.today
CVE Published
Aug 27, 2026 - 10:40 cve.org
CRITICAL 9.3

DescriptionCVE.org

Zbtlink WE1326, WE357, WE5926, WE5926-WD, WE826-Q, WE826-T2, WE826-WD, WG108, and WG3526 firmware 19.1101, Zbtlink WE2426-C firmware 19.1112, Zbtlink WE5926-EC_QP firmware 20.0516, Zbtlink WF3526-P firmware 19.051, CTN720-W1, LF-1541, and MT7620N firmware 19.1101, and WRC1 firmware 20.0622 contain an unauthenticated command injection in the infosrvd service (UDP/9992). A remote unauthenticated attacker can send a crafted UDP packet to execute arbitrary commands as root. The service's authentication uses a hardcoded salt and an all-zero wildcard MAC bypass, rendering it ineffective.

AnalysisAI

Remote unauthenticated command execution affects a broad range of Zbtlink MT7620-based routers and gateways (WE1326, WE2426-C, WE5926 family, WE826 family, WG108/WG3526, WF3526-P, CTN720-W1, LF-1541, MT7620N, WRC1) whose infosrvd service listens on UDP/9992. A single crafted UDP packet lets an attacker run arbitrary commands as root, because the service's authentication relies on a hardcoded salt and accepts an all-zero wildcard MAC, defeating the intended check. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access
Scan for exposed UDP/9992 infosrvd
Delivery
Send crafted packet with all-zero MAC
Exploit
Bypass hardcoded-salt authentication
Execution
Inject shell command
Persist
Execute arbitrary commands as root
Impact
Pivot or enlist device into botnet
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Vulnerability AssessmentAI

Exploitation Exploitation requires network reachability to the infosrvd service on UDP port 9992 on an affected Zbtlink device running the listed firmware; the attacker abuses the service's hardcoded salt and all-zero wildcard MAC authentication bypass, so no valid credentials, user interaction, or non-default configuration are needed (AV:N/AC:L/AT:N/PR:N/UI:N). … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment This is a genuine high-priority issue rather than an inflated CVSS score. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario An attacker scans for internet-reachable Zbtlink routers exposing UDP/9992, then sends a single crafted infosrvd packet using the all-zero wildcard MAC and hardcoded-salt-derived value to pass authentication. The packet carries an injected shell command that infosrvd executes as root, giving the attacker immediate full control of the device - enabling traffic interception, pivoting into the internal network, or enrollment into a botnet. …
Remediation No vendor-released patch or fixed firmware version was identified in the provided data at time of analysis, so remediation should center on compensating controls until Zbtlink publishes updated firmware - monitor the VulnCheck advisory (https://www.vulncheck.com/advisories/zbtlink-mqwrt-infosrvd-command-injection) and Zbtlink support channels for a fixed build. … Detailed patch versions, workarounds, and compensating controls in full report.
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Recommended ActionAI

Within 24 hours, conduct a network asset scan to identify all Zbtlink MT7620-based routers and gateways by model number across your infrastructure and document their network locations and criticality. …

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CVE-2026-74233 vulnerability details – vuln.today
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