CVE-2013-5143 in Mac OS X Server
Summary
by MITRE
The RADIUS service in Server App in Apple OS X Server before 3.0 selects a fallback X.509 certificate in unspecified circumstances, which might allow man-in-the-middle attackers to hijack RADIUS sessions by leveraging knowledge of the private key that matches this fallback certificate.
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Analysis
by VulDB Data Team • 06/01/2021
The vulnerability described in CVE-2013-5143 represents a critical security flaw in Apple's OS X Server RADIUS service implementation. This issue specifically affects versions prior to 3.0 and stems from improper certificate selection mechanisms within the RADIUS authentication process. The vulnerability manifests when the RADIUS service encounters circumstances where it must fall back to a secondary X.509 certificate for authentication purposes, creating an exploitable condition that undermines the security of wireless and network authentication sessions.
The technical root cause of this vulnerability lies in the certificate selection algorithm used by the RADIUS service during authentication negotiations. When the primary certificate fails or cannot be properly validated, the system automatically reverts to a fallback certificate without proper validation of the certificate chain or trust parameters. This fallback mechanism operates under unspecified circumstances, making it difficult for administrators to predict or prevent the condition. The vulnerability is particularly dangerous because it allows attackers to perform man-in-the-middle attacks by leveraging knowledge of the private key associated with the fallback certificate, effectively compromising the integrity of the entire authentication process.
From an operational impact perspective, this vulnerability exposes organizations to significant risks in environments that rely on RADIUS authentication for wireless networks, VPN access, and network device authentication. Attackers who can obtain the private key matching the fallback certificate can intercept and manipulate RADIUS authentication exchanges, potentially gaining unauthorized access to network resources, eavesdropping on authenticated sessions, or conducting session hijacking attacks. The vulnerability affects the fundamental security posture of networks using Apple OS X Server as their authentication infrastructure, particularly in enterprise environments where wireless access and secure network authentication are critical components of the security architecture.
The security implications extend beyond simple authentication bypasses, as this vulnerability can be leveraged to establish persistent access points within network infrastructure. According to CWE classification, this represents a weakness in the certificate validation process and improper certificate selection, falling under the category of weak cryptographic key usage. From an ATT&CK framework perspective, this vulnerability maps to techniques involving credential access through man-in-the-middle attacks and privilege escalation via authentication manipulation. Organizations should implement immediate mitigations including upgrading to OS X Server version 3.0 or later, implementing additional network monitoring for suspicious authentication patterns, and ensuring proper certificate management practices to prevent unauthorized certificate deployment.
The vulnerability highlights the importance of robust certificate management and validation processes in authentication systems, particularly when fallback mechanisms are implemented. Security practitioners should conduct thorough assessments of their RADIUS infrastructure to identify potential exposure to similar certificate selection flaws and implement comprehensive monitoring solutions to detect anomalous authentication behavior. Regular security audits of certificate deployment and validation procedures become essential to prevent exploitation of similar vulnerabilities in other authentication systems. Organizations must also consider implementing additional layers of security such as network segmentation, enhanced monitoring of authentication traffic, and regular penetration testing to identify potential exploitation vectors before they can be leveraged by malicious actors.