CVE-2016-20031 in ZKBioSecurity
Summary
by MITRE • 03/16/2026
ZKTeco ZKBioSecurity 3.0 contains a local authorization bypass vulnerability in visLogin.jsp that allows attackers to authenticate without valid credentials by spoofing localhost requests. Attackers can exploit the EnvironmentUtil.getClientIp() method which treats IPv6 loopback address 0:0:0:0:0:0:0:1 as 127.0.0.1 and authenticates using the IP as username with hardcoded password 123456 to access sensitive information and perform unauthorized actions.
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Analysis
by VulDB Data Team • 03/16/2026
The vulnerability identified as CVE-2016-20031 resides within the ZKTeco ZKBioSecurity 3.0 security solution, specifically targeting the visLogin.jsp component that handles user authentication processes. This critical authorization bypass flaw represents a significant security weakness in the system's access control mechanisms, potentially allowing unauthorized individuals to gain administrative privileges without proper authentication credentials. The vulnerability stems from a fundamental flaw in how the application processes client IP address information during the authentication workflow, creating an exploitable condition that undermines the entire security framework.
The technical root cause of this vulnerability lies in the EnvironmentUtil.getClientIp() method implementation which fails to properly distinguish between IPv6 and IPv4 loopback addresses. When an attacker crafts a request that appears to originate from the localhost, the system incorrectly interprets the IPv6 loopback address 0:0:0:0:0:0:0:1 as the IPv4 equivalent 127.0.0.1. This misinterpretation triggers an authentication mechanism that automatically uses the IP address as the username parameter and attempts to authenticate using a hardcoded password of 123456. This approach violates fundamental security principles by relying on default credentials and failing to properly validate or sanitize input parameters, creating a path for unauthorized access to sensitive system resources.
The operational impact of this vulnerability extends far beyond simple unauthorized access, as it enables attackers to perform a wide range of malicious activities within the compromised system. Once authenticated through this bypass mechanism, an attacker can access sensitive information including user credentials, biometric data, system configurations, and administrative controls. The vulnerability allows for privilege escalation and persistent access to the security solution, potentially enabling attackers to modify system settings, disable security features, or extract confidential data. This represents a severe compromise of the system's integrity and confidentiality, as the hardcoded password provides no meaningful security barrier against determined attackers who can exploit this weakness repeatedly.
The vulnerability aligns with CWE-287 which addresses improper authentication issues, specifically targeting the weakness of using default credentials and flawed IP address handling. From an attacker perspective, this flaw maps to multiple ATT&CK techniques including T1078 for valid accounts and T1566 for social engineering through IP spoofing. The attack vector involves crafting HTTP requests that appear to originate from localhost, leveraging the system's trust in loopback addresses to bypass normal authentication controls. Organizations implementing this security solution face significant risk of unauthorized access, data breaches, and potential system compromise that could affect physical security infrastructure and biometric access controls.
Mitigation strategies should focus on implementing proper IP address validation and sanitization within the authentication process, ensuring that loopback addresses are handled appropriately regardless of their IPv6 or IPv4 representation. System administrators should immediately update to patched versions of ZKBioSecurity 3.0 that address this specific vulnerability, while also implementing network segmentation to limit direct access to authentication endpoints. Additional protective measures include disabling unnecessary services, implementing proper firewall rules to restrict access to authentication interfaces, and conducting regular security assessments to identify similar implementation flaws. The vulnerability demonstrates the critical importance of proper input validation and authentication design, emphasizing that default credentials and overly trusting IP address handling should never be part of production security systems.