CVE-2014-2188 in IOS
Summary
by MITRE
The Authentication Proxy feature in Cisco IOS does not properly handle invalid AAA return codes from RADIUS and TACACS+ servers, which allows remote attackers to bypass authentication in opportunistic circumstances via a connection attempt that triggers an invalid code, as demonstrated by a connection attempt with a blank password, aka Bug IDs CSCuo09400 and CSCun16016.
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Analysis
by VulDB Data Team • 03/10/2022
The vulnerability identified as CVE-2014-2188 represents a critical authentication bypass flaw within Cisco IOS operating systems that affects the Authentication Proxy feature. This issue stems from improper handling of invalid AAA return codes generated by RADIUS and TACACS+ authentication servers, creating a security gap that adversaries can exploit under specific conditions. The vulnerability manifests when authentication proxy components receive malformed or unexpected responses from backend authentication servers, leading to inconsistent authentication behavior that can be manipulated by remote attackers.
The technical flaw resides in the authentication proxy implementation where Cisco IOS fails to properly validate and process AAA return codes from authentication servers. When RADIUS or TACACS+ servers return invalid or unexpected status codes, the authentication proxy does not handle these responses gracefully but instead allows the connection to proceed without proper authentication verification. This behavior creates an opportunistic attack vector where attackers can craft specific connection attempts that trigger the vulnerable code path, particularly when using blank passwords or other malformed authentication credentials that cause the backend servers to return unexpected responses.
The operational impact of this vulnerability extends beyond simple authentication bypass to potentially compromise entire network access control mechanisms. Attackers exploiting this vulnerability can gain unauthorized access to network devices without proper credentials, potentially escalating their privileges and accessing sensitive network resources. The vulnerability is particularly concerning because it operates silently, allowing unauthorized access without generating typical authentication failure alerts, making detection more challenging for network security monitoring systems. This type of vulnerability directly impacts the CIA triad by weakening authentication controls and potentially enabling data integrity violations.
Security professionals should implement immediate mitigations including updating Cisco IOS software to versions that address the authentication proxy handling issues, configuring proper AAA server failover mechanisms, and implementing additional access controls such as SSH key-based authentication or certificate-based authentication. Network segmentation and monitoring of authentication proxy activities should be enhanced to detect anomalous authentication patterns. This vulnerability aligns with CWE-284 which addresses improper access control and relates to ATT&CK technique T1078 for valid accounts and T1566 for social engineering attacks that leverage authentication bypasses. Organizations should also review their authentication server configurations to ensure proper error handling and implement robust logging mechanisms to track authentication proxy behavior and detect potential exploitation attempts.