CVE-2004-2163 in OpenBSD
Summary
by MITRE
login_radius on OpenBSD 3.2, 3.5, and possibly other versions does not verify the shared secret in a response packet from a RADIUS server, which allows remote attackers to bypass authentication by spoofing server replies.
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Analysis
by VulDB Data Team • 06/29/2019
The vulnerability identified as CVE-2004-2163 affects the login_radius component in OpenBSD versions 3.2 and 3.5, representing a critical authentication bypass flaw that undermines the security of RADIUS-based network access control systems. This issue specifically targets the RADIUS authentication protocol implementation within the OpenBSD operating system, where the login_radius utility fails to validate the shared secret contained within response packets received from RADIUS servers. The flaw exists at the protocol validation layer where the system should verify the integrity of responses through cryptographic verification of the shared secret but instead accepts all responses without proper authentication checks.
The technical implementation of this vulnerability stems from improper validation of RADIUS response packets in the authentication process. When a user attempts to authenticate through a RADIUS server, the server responds with a packet containing authentication results and a shared secret for verification. The login_radius utility in affected OpenBSD versions processes these responses without performing the required cryptographic validation of the shared secret field, allowing malicious actors to craft spoofed response packets that appear legitimate to the client system. This weakness directly violates the fundamental security principle of mutual authentication in network protocols and creates an exploitable condition where unauthorized users can gain access to network resources without proper credentials.
The operational impact of this vulnerability extends beyond simple authentication bypass to potentially compromise entire network access control systems. Attackers can leverage this flaw to impersonate legitimate RADIUS servers and grant unauthorized access to network resources, effectively neutralizing the security benefits of RADIUS authentication. The vulnerability affects the integrity and confidentiality of network access controls, as it allows attackers to bypass the authentication mechanisms that are supposed to verify user credentials before granting access. This represents a significant weakness in the network security infrastructure, particularly in environments where RADIUS authentication is critical for access control and network segmentation.
Security professionals should recognize this vulnerability as a classic example of insufficient input validation and authentication verification, aligning with CWE-287 which addresses improper handling of authentication tokens and credentials. The attack vector demonstrates characteristics consistent with MITRE ATT&CK technique T1078 for valid accounts and T1566 for phishing, as attackers can exploit this weakness to gain unauthorized system access through spoofed authentication responses. Organizations should implement immediate mitigations including updating to patched versions of OpenBSD, implementing network segmentation to isolate RADIUS servers, and deploying additional authentication layers. The vulnerability highlights the importance of cryptographic verification in authentication protocols and underscores the critical need for proper shared secret validation in network security implementations. Network administrators must also consider implementing monitoring solutions to detect anomalous authentication patterns that might indicate exploitation attempts.