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CVE-2016-20030

| EUVD-2016-10815 CRITICAL
Incorrect Behavior Order: Authorization Before Parsing and Canonicalization (CWE-551)
2026-03-15 VulnCheck
9.3
CVSS 4.0
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CVSS VectorNVD

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

5
CVSS changed
Apr 15, 2026 - 15:22 NVD
9.8 (CRITICAL) 9.3 (CRITICAL)
PoC Detected
Mar 16, 2026 - 14:53 vuln.today
Public exploit code
EUVD ID Assigned
Mar 15, 2026 - 14:00 euvd
EUVD-2016-10815
Analysis Generated
Mar 15, 2026 - 14:00 vuln.today
CVE Published
Mar 15, 2026 - 13:35 nvd
CRITICAL 9.8

DescriptionNVD

ZKTeco ZKBioSecurity 3.0 contains a user enumeration vulnerability that allows unauthenticated attackers to discover valid usernames by submitting partial characters via the username parameter. Attackers can send requests to the authLoginAction!login.do script with varying username inputs to enumerate valid user accounts based on application responses.

AnalysisAI

User enumeration vulnerability in ZKTeco ZKBioSecurity 3.0 that allows unauthenticated attackers to discover valid usernames through partial character submissions to the authentication endpoint. A public proof-of-concept exploit is available, making this vulnerability actively exploitable, though it has a notably high CVSS score of 9.8 that appears inflated given the actual impact is limited to information disclosure.

Technical ContextAI

The vulnerability affects ZKTeco ZKBioSecurity version 3.0 (CPE: cpe:2.3:a:zkteco_inc.:zkteco_zkbiosecurity:*:*:*:*:*:*:*:*), a biometric security management system. The root cause is CWE-551 (Incorrect Behavior Order: Authorization Before Parsing and Canonicalization), where the authLoginAction!login.do script responds differently to partial username inputs, allowing attackers to enumerate valid accounts. This is a classic timing/response-based enumeration flaw in the authentication mechanism.

RemediationAI

No specific patch information is available in the provided references. Organizations should: 1) Contact ZKTeco for an updated version that addresses this vulnerability, 2) Implement rate limiting on the authentication endpoint, 3) Ensure consistent error messages regardless of username validity, 4) Monitor authentication logs for enumeration attempts. The vendor advisory link (https://www.vulncheck.com/advisories/zkteco-zkbiosecurity-user-enumeration-via-authloginaction) should be consulted for official guidance.

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CVE-2016-20030 vulnerability details – vuln.today

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