CVE-2015-4237 in NX-OS
Summary
by MITRE
The CLI parser in Cisco NX-OS 4.1(2)E1(1), 6.2(11b), 6.2(12), 7.2(0)ZZ(99.1), 7.2(0)ZZ(99.3), and 9.1(1)SV1(3.1.8) on Nexus devices allows local users to execute arbitrary OS commands via crafted characters in a filename, aka Bug IDs CSCuv08491, CSCuv08443, CSCuv08480, CSCuv08448, CSCuu99291, CSCuv08434, and CSCuv08436.
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Analysis
by VulDB Data Team • 05/23/2022
The vulnerability identified as CVE-2015-4237 represents a critical command injection flaw within the Command Line Interface parser of Cisco NX-OS operating system versions spanning multiple release branches. This issue affects a range of Nexus switching platforms where the CLI parser fails to properly sanitize user input when processing filenames containing specially crafted characters. The vulnerability manifests as a local privilege escalation vector that allows authenticated users with access to the device to execute arbitrary operating system commands with elevated privileges. The flaw specifically occurs during filename parsing operations where input validation mechanisms are insufficient to prevent malicious character sequences from being interpreted as command instructions rather than simple file path references.
The technical exploitation of this vulnerability stems from improper input validation within the CLI parsing subsystem, which constitutes a classic command injection weakness classified under CWE-78 as "Improper Neutralization of Special Elements used in an OS Command." The affected Cisco NX-OS versions demonstrate a failure in implementing proper sanitization of user-supplied data before it is processed by the underlying operating system shell. Attackers can craft filenames containing shell metacharacters such as semicolons, pipes, or command concatenation operators that bypass normal input validation checks and are subsequently executed by the system's command processing engine. This vulnerability operates at the operating system level rather than the application level, making it particularly dangerous as it can be leveraged to execute system commands with the privileges of the executing process, typically root or administrative access.
The operational impact of CVE-2015-4237 extends beyond simple unauthorized command execution to potentially compromise entire network infrastructure deployments. Network administrators utilizing affected Nexus switches face significant risk of unauthorized access and potential system compromise, as the vulnerability allows for arbitrary code execution without requiring additional privileges beyond local access to the device. The attack surface includes any scenario where users can interact with the CLI parser, including legitimate administrative operations that involve file operations or configuration management. This vulnerability directly maps to ATT&CK technique T1059.001 for Command and Scripting Interpreter and T1068 for Exploitation for Privilege Escalation, representing both execution and privilege escalation vectors. Organizations with extensive Cisco Nexus deployments across their network infrastructure face substantial risk of unauthorized access to core network devices, potentially enabling attackers to modify configurations, exfiltrate sensitive data, or establish persistent access points within their network environments.
Mitigation strategies for this vulnerability require immediate patching of affected Cisco NX-OS versions through official software updates provided by Cisco Security Advisory. Organizations should implement network segmentation and access controls to limit local administrative access to network devices, reducing the attack surface for potential exploitation. The implementation of input validation controls and monitoring of CLI usage patterns can help detect anomalous behavior indicative of exploitation attempts. Network administrators should also consider disabling unnecessary CLI features and implementing strict access controls to limit the number of users with local administrative privileges. Additionally, regular security audits and vulnerability assessments should be conducted to identify other potential command injection vulnerabilities within network infrastructure components, as this vulnerability demonstrates the importance of proper input validation in network operating system implementations. The affected versions should be upgraded to patched releases that address the specific CLI parsing flaws, with Cisco recommending immediate deployment of security updates to prevent exploitation by malicious actors.