CVE-2006-1354 in FreeRADIUS
Summary
by MITRE
Unspecified vulnerability in FreeRADIUS 1.0.0 up to 1.1.0 allows remote attackers to bypass authentication or cause a denial of service (server crash) via "Insufficient input validation" in the EAP-MSCHAPv2 state machine module.
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Analysis
by VulDB Data Team • 06/16/2019
The vulnerability identified as CVE-2006-1354 resides within the FreeRADIUS authentication server software version 1.0.0 through 1.1.0, specifically affecting the EAP-MSCHAPv2 state machine module. This represents a critical security flaw that stems from inadequate input validation mechanisms within the authentication protocol implementation. The issue manifests when the system processes EAP-MSCHAPv2 authentication requests, which are commonly used in wireless network security and remote access scenarios where Microsoft Challenge Handshake Authentication Protocol version 2 serves as the primary authentication mechanism.
The technical flaw constitutes a classic input validation weakness that enables malicious actors to exploit the EAP-MSCHAPv2 state machine through malformed or insufficiently validated data inputs. This vulnerability operates at the protocol level where the FreeRADIUS server fails to properly validate the state transitions and data processing within the EAP-MSCHAPv2 authentication flow. The insufficient validation allows attackers to craft specially crafted authentication packets that can either bypass the authentication process entirely or force the server into an unstable state that results in service disruption. This type of vulnerability aligns with CWE-20, which categorizes improper input validation as a fundamental weakness in software security design.
The operational impact of this vulnerability extends beyond simple authentication bypass scenarios to include potential denial of service conditions that can severely disrupt network access services. When exploited for denial of service, the vulnerability can cause the FreeRADIUS server to crash or become unresponsive, effectively cutting off legitimate users from accessing network resources. In authentication bypass scenarios, attackers can gain unauthorized access to protected network segments, potentially leading to data breaches, privilege escalation, and unauthorized network penetration. The vulnerability affects enterprise environments that rely on FreeRADIUS for wireless network authentication, VPN services, and remote access solutions where EAP-MSCHAPv2 is implemented.
From a threat modeling perspective, this vulnerability maps to several ATT&CK techniques including T1110.003 for credential access through brute force and T1499.004 for network disruption via resource exhaustion. The attack surface is particularly concerning given that EAP-MSCHAPv2 is widely deployed in corporate wireless networks and remote access infrastructures, making this vulnerability attractive to adversaries seeking persistent network access. Organizations using FreeRADIUS versions within the affected range face significant risk exposure, particularly in environments where wireless network security is critical and where the availability of authentication services directly impacts business continuity. The vulnerability demonstrates how insufficient validation in protocol implementations can create cascading security issues that compromise both confidentiality and availability of network services.
The recommended mitigations include immediate upgrade to FreeRADIUS version 1.1.1 or later where this vulnerability has been addressed through proper input validation mechanisms. System administrators should also implement network monitoring to detect anomalous authentication patterns that might indicate exploitation attempts. Additionally, network segmentation and access controls should be reviewed to limit the potential impact of successful exploitation, while regular security assessments should be conducted to identify similar validation gaps in other network services and protocols. The fix implemented in subsequent versions demonstrates the importance of robust input validation in security-critical components and serves as a reminder of the potential consequences when such validation is omitted or insufficiently implemented in authentication systems.