CVE-2018-0185 in IOS XE
Summary
by MITRE
Multiple vulnerabilities in the CLI parser of Cisco IOS XE Software could allow an authenticated, local attacker to inject arbitrary commands into the CLI of the affected software, which could allow the attacker to gain access to the underlying Linux shell of an affected device and execute commands with root privileges on the device. The vulnerabilities exist because the affected software does not sufficiently sanitize command arguments before passing commands to the Linux shell for execution. An attacker could exploit these vulnerabilities by submitting a malicious CLI command to the affected software. A successful exploit could allow the attacker to break from the CLI of the affected software, which could allow the attacker to gain access to the underlying Linux shell on an affected device and execute arbitrary commands with root privileges on the device. Cisco Bug IDs: CSCuz03145, CSCuz56419, CSCva31971, CSCvb09542.
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Analysis
by VulDB Data Team • 01/17/2020
The vulnerability identified as CVE-2018-0185 represents a critical command injection flaw within the Command Line Interface parser of Cisco IOS XE Software, classified under CWE-78 as improper input validation. This security weakness affects multiple Cisco devices running IOS XE software, creating a pathway for authenticated local attackers to escalate privileges and gain root access to the underlying Linux shell. The vulnerability stems from insufficient sanitization of command arguments before these inputs are processed and passed to the Linux shell for execution, creating an environment where malicious input can be interpreted as legitimate shell commands rather than simple user input. The affected software fails to properly validate or escape special characters and shell metacharacters that could alter the intended execution flow of commands.
Attackers exploiting this vulnerability can leverage the CLI parser's weakness to inject arbitrary commands that bypass normal security controls and access the underlying operating system. The exploitation process involves crafting malicious CLI commands that manipulate the parser into executing unintended shell operations, effectively allowing attackers to escape the restricted CLI environment and gain direct access to the Linux shell where they can execute commands with full administrative privileges. This type of attack aligns with ATT&CK technique T1059.004 for command and scripting interpreter, specifically targeting the Linux shell environment. The vulnerability is particularly dangerous because it requires only local authentication, meaning that an attacker with legitimate access credentials can exploit this weakness to escalate their privileges without requiring additional attack vectors or external network access.
The operational impact of CVE-2018-0185 extends beyond simple privilege escalation, as it fundamentally compromises the security posture of affected Cisco devices by providing attackers with complete control over the underlying Linux environment. Once an attacker gains root access through this vulnerability, they can modify system files, install backdoors, access sensitive data, and potentially use the compromised device as a pivot point for attacking other systems within the network. The attack surface is significant since the vulnerability affects the core CLI functionality that administrators rely on for device management, making it a prime target for adversaries seeking persistent access to network infrastructure. This vulnerability also undermines the principle of least privilege and the security model that relies on the CLI as a controlled interface for system administration.
Mitigation strategies for CVE-2018-0185 should focus on immediate patching of affected IOS XE software versions, as Cisco released security advisories and patches addressing the specific command injection flaws. Network administrators should implement strict access controls and monitoring for CLI usage, particularly for commands that might trigger shell execution. The remediation process involves updating to Cisco IOS XE software versions that properly sanitize command arguments and implement proper input validation before shell execution. Organizations should also consider implementing network segmentation and access controls to limit local administrative access to devices, reducing the attack surface for local privilege escalation attacks. Additionally, security monitoring solutions should be configured to detect unusual CLI command patterns that might indicate exploitation attempts, providing an additional layer of defense against potential attackers leveraging this vulnerability.