CVE-2012-4122 in NX-OS
Summary
by MITRE
The CLI parser in Cisco NX-OS allows local users to bypass intended access restrictions, and overwrite or create arbitrary files, via shell output redirection, aka Bug IDs CSCts56672 and CSCts56669.
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Analysis
by VulDB Data Team • 03/15/2019
The vulnerability identified as CVE-2012-4122 represents a critical security flaw within the Command Line Interface parser of Cisco NX-OS operating system versions. This issue affects network devices running Cisco NX-OS software and stems from improper handling of shell output redirection commands within the CLI environment. The vulnerability is particularly concerning because it allows local authenticated users to escalate their privileges and bypass intended access controls that are typically enforced by the operating system.
The technical implementation of this vulnerability resides in the insufficient sanitization of command-line arguments within the NX-OS CLI parser. When users execute commands through the CLI interface, the system fails to properly validate or escape special shell characters that enable output redirection. This allows maliciously crafted commands to bypass normal access controls and potentially overwrite or create arbitrary files on the system. The flaw specifically manifests when users leverage shell redirection operators such as >, >>, or < within CLI commands, which should normally be restricted or properly escaped by the system's security controls. This weakness creates a path for privilege escalation and arbitrary file manipulation that directly violates the principle of least privilege and proper access control enforcement.
The operational impact of this vulnerability extends beyond simple file manipulation capabilities. Local users who can access the CLI interface can exploit this flaw to gain unauthorized access to system resources, potentially leading to complete system compromise. Attackers could use this vulnerability to modify critical system files, create backdoor accounts, or install malicious software that persists across system reboots. The vulnerability affects Cisco NX-OS versions running on various network switches and routers, making it particularly dangerous in enterprise environments where these devices form the backbone of network infrastructure. The implications are severe because network administrators typically trust CLI access within their network devices, making this a stealthy attack vector that could go undetected for extended periods.
Security professionals should consider this vulnerability in the context of the MITRE ATT&CK framework, specifically mapping it to techniques related to privilege escalation and persistence. The vulnerability aligns with CWE-78, which describes improper neutralization of special elements used in OS commands, and CWE-22, which addresses improper limitation of a pathname to a restricted directory. Organizations should implement immediate mitigations including applying the latest Cisco security patches and advisories, restricting CLI access to only necessary administrative users, and implementing comprehensive monitoring for unusual file creation or modification activities. Network segmentation and privilege management should be reviewed to ensure that local access to CLI interfaces is strictly controlled and monitored, as this vulnerability essentially undermines the trust model that normally governs CLI access within network infrastructure devices.