CVE-2014-0739 in ASA
Summary
by MITRE
Race condition in the Phone Proxy component in Cisco Adaptive Security Appliance (ASA) Software 9.1(.3) and earlier allows remote attackers to bypass sec_db authentication and provide certain pass-through services to untrusted devices via a crafted configuration-file TFTP request, aka Bug ID CSCuj66766.
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Analysis
by VulDB Data Team • 05/24/2017
The vulnerability described in CVE-2014-0739 represents a critical race condition within the Phone Proxy component of Cisco Adaptive Security Appliance (ASA) Software versions 9.1.3 and earlier. This flaw exists in the manner in which the system processes TFTP requests during the authentication phase, creating a window where unauthorized access can occur. The vulnerability specifically affects the sec_db authentication mechanism that is designed to validate and authorize devices attempting to utilize pass-through services through the ASA appliance. The race condition occurs when multiple processes attempt to access shared resources simultaneously without proper synchronization, allowing malicious actors to exploit this temporal gap in the authentication workflow.
The technical implementation of this vulnerability involves a carefully crafted configuration file TFTP request that triggers the race condition in the Phone Proxy component. When an attacker sends such a request, the system's authentication process becomes vulnerable to timing-based exploitation where the security database validation occurs concurrently with other operations. This creates an opportunity for untrusted devices to bypass the normal authentication procedures and gain access to services that should only be available to authenticated and authorized systems. The flaw essentially allows for a temporal inconsistency in the security validation process, where the system's internal state becomes unpredictable during the critical authentication window.
From an operational impact perspective, this vulnerability enables remote attackers to gain unauthorized access to pass-through services that are typically restricted to trusted devices within the network infrastructure. The implications extend beyond simple unauthorized access, as the compromised system could potentially allow attackers to manipulate network traffic, gain further access to internal systems, or disrupt normal network operations. The vulnerability affects network security posture significantly since it undermines the fundamental authentication mechanisms that are supposed to protect enterprise networks from unauthorized access attempts. Organizations relying on Cisco ASA appliances for network security could experience complete compromise of their network access controls if this vulnerability is exploited.
The vulnerability maps directly to CWE-367, which identifies Time-of-Check to Time-of-Use (TOCTOU) race conditions as a critical security weakness. This classification aligns with the nature of the flaw where the system's validation occurs at one point in time but the actual access decision happens at a different moment, creating an exploitable gap. From an ATT&CK framework perspective, this vulnerability corresponds to techniques involving privilege escalation and initial access through network service exploitation. The attack vector leverages remote network connectivity to exploit the timing inconsistency, which falls under the T1190 - Exploit Public-Facing Application technique category. Organizations should implement immediate mitigations including applying Cisco's security patches, implementing network segmentation to limit exposure, and monitoring for anomalous TFTP traffic patterns that could indicate exploitation attempts.
The remediation approach for this vulnerability requires immediate deployment of Cisco's official security patches and updates to ASA software versions that address the specific race condition in the Phone Proxy component. Network administrators should also consider implementing additional controls such as disabling unnecessary TFTP services, restricting TFTP access to trusted networks only, and deploying intrusion detection systems that can identify suspicious TFTP request patterns. The vulnerability demonstrates the critical importance of proper synchronization mechanisms in security-critical code components and highlights the need for thorough testing of concurrent access scenarios in network security appliances. Organizations should conduct comprehensive security assessments to ensure that similar timing-based vulnerabilities do not exist in other components of their network infrastructure, as these types of race conditions can often be found in complex security systems where multiple processes interact with shared resources.