CVE-2012-4078 in Unified Computing System
Summary
by MITRE
The Baseboard Management Controller (BMC) in Cisco Unified Computing System (UCS) does not properly handle SSH escape sequences, which allows remote authenticated users to bypass an unspecified authentication step via SSH port forwarding, aka Bug ID CSCtg17656.
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Analysis
by VulDB Data Team • 01/07/2022
The vulnerability identified as CVE-2012-4078 affects the Baseboard Management Controller component within Cisco Unified Computing System environments, representing a critical security weakness in remote management infrastructure. This flaw exists within the SSH implementation of the BMC subsystem, which serves as the primary interface for out-of-band management of Cisco UCS servers. The vulnerability specifically targets the handling of SSH escape sequences, which are special character combinations used to control SSH sessions and facilitate various operational functions including port forwarding and session management. The affected BMC implementation fails to properly validate or process these escape sequences, creating an exploitable condition that undermines the authentication mechanisms designed to secure remote access to the management interface.
The technical exploitation of this vulnerability occurs through the manipulation of SSH escape sequences during authenticated SSH sessions to the BMC. Attackers with valid credentials can leverage this flaw to bypass an unspecified authentication step, effectively gaining unauthorized access to additional system resources or functions that should otherwise remain protected. The vulnerability is particularly concerning because it operates within the SSH port forwarding mechanism, which is a standard feature used for secure tunneling of network connections. This allows attackers to potentially establish unauthorized connections to internal systems or bypass network segmentation controls that would normally protect sensitive infrastructure components. The flaw essentially creates a backdoor path through the authentication process, enabling attackers to escalate their privileges or access additional management functions without proper authorization.
The operational impact of this vulnerability extends beyond simple unauthorized access, as it can enable attackers to compromise the entire management infrastructure of Cisco UCS deployments. This represents a significant risk to enterprise security posture since the BMC serves as a critical management interface for server hardware, often containing sensitive configuration data, firmware images, and access credentials for the entire system. The vulnerability can be exploited by authenticated users who are already within the network perimeter, making it particularly dangerous in environments where network segmentation is not properly implemented. This type of vulnerability aligns with CWE-284, which addresses improper access control, and can be categorized under ATT&CK technique T1078 for valid accounts and T1562 for evasion techniques. The impact is further amplified by the fact that BMC management interfaces are often overlooked in security assessments, making this vulnerability particularly stealthy and difficult to detect.
Organizations affected by this vulnerability should implement immediate mitigations including updating to Cisco software releases that address the specific SSH escape sequence handling flaw, typically through security patches or firmware updates provided by Cisco. Network administrators should also consider implementing additional access controls and monitoring for unusual SSH activity patterns, particularly around port forwarding operations and escape sequence usage. The vulnerability highlights the importance of proper input validation and secure coding practices in network management interfaces, as the flaw demonstrates how seemingly minor implementation details in protocol handling can create significant security risks. Additionally, organizations should review their overall security architecture to ensure that BMC management interfaces are properly segmented from production networks and that access controls are appropriately enforced. Regular security assessments should include testing of management interfaces for similar vulnerabilities, and network monitoring should be enhanced to detect anomalous SSH behavior that could indicate exploitation attempts. This vulnerability serves as a reminder of the critical importance of secure implementation of standard network protocols, particularly in management and administrative interfaces where the consequences of exploitation can be severe and far-reaching.