CVE-2012-4121 in NX-OS
Summary
by MITRE
Cisco NX-OS allows local users to gain privileges, and read or modify arbitrary files, via the sed (1) r and (2) w commands, aka Bug IDs CSCts56559, CSCts56565, CSCts56570, and CSCts56574.
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Analysis
by VulDB Data Team • 05/26/2021
The vulnerability identified as CVE-2012-4121 affects Cisco NX-OS operating systems and represents a critical privilege escalation and arbitrary file access flaw. This vulnerability specifically targets the sed command implementation within the network operating system, creating a pathway for local attackers to escalate their privileges from standard user levels to administrative access. The flaw manifests through two distinct command variants within the sed utility: the r command and the w command, both of which are susceptible to exploitation. These commands are commonly used for text processing and file manipulation within Unix-like systems, making their exploitation particularly dangerous as they can be leveraged to execute malicious code or modify system-critical files. The vulnerability was catalogued under multiple Bug IDs including CSCts56559, CSCts56565, CSCts56570, and CSCts56574, indicating the complexity and severity of the issue across different system components. This type of vulnerability falls under the Common Weakness Enumeration category CWE-264, which encompasses permissions, privileges, and access control weaknesses. The impact of this vulnerability extends beyond simple privilege escalation as it enables attackers to read or modify arbitrary files on the system, potentially compromising the integrity and confidentiality of network device configurations and sensitive data. The operational impact is severe for organizations relying on Cisco NX-OS for their network infrastructure, as compromised devices could lead to complete network control and unauthorized access to critical network resources.
The technical exploitation of this vulnerability involves leveraging the sed command's r and w functionality to manipulate file access permissions and execute code with elevated privileges. When local users execute specific sed commands with malicious parameters, they can bypass normal access controls and gain unauthorized access to system files that should be restricted. The r command, typically used for reading files, and the w command, used for writing files, both contain implementation flaws that allow attackers to manipulate file paths and access control mechanisms. This vulnerability demonstrates a classic case of insecure file handling within system utilities, where proper input validation and access control checks are insufficiently implemented. The flaw essentially allows attackers to perform file operations that should be restricted to system administrators, creating a path for privilege escalation attacks. From an attack perspective, this vulnerability aligns with the MITRE ATT&CK framework's privilege escalation techniques, specifically targeting the 'Local Port' and 'File and Directory Permissions Modification' tactics. The exploitation requires minimal privileges initially, making it particularly dangerous as attackers can start with standard user access and escalate to root or administrative levels through these commands.
Organizations utilizing Cisco NX-OS systems face significant operational risks when this vulnerability remains unpatched, as it creates persistent access points for malicious actors to compromise network infrastructure. The ability to read arbitrary files means attackers can potentially extract sensitive configuration data, authentication credentials, or other critical information stored on the network devices. Additionally, the capability to modify files allows for persistent backdoor installation, configuration changes that could disrupt network operations, or data corruption that could lead to service degradation. The vulnerability's impact is amplified in environments where network devices are not properly segmented or monitored, as attackers could use compromised devices as entry points to access other network segments. Security professionals should consider implementing network segmentation strategies and monitoring for unusual file access patterns as part of their defensive measures. The vulnerability also highlights the importance of regular security updates and patch management processes, as Cisco has released patches addressing these specific issues in their NX-OS software releases. Organizations should also review their access control policies and implement principle of least privilege configurations to minimize the potential impact if such vulnerabilities are exploited. The incident underscores the necessity of comprehensive security testing of system utilities and the importance of validating input parameters in commands that handle file operations. From a compliance perspective, this vulnerability could result in violations of security standards such as those outlined in ISO 27001, NIST SP 800-53, and other regulatory frameworks requiring proper access controls and system integrity protection.