CVE-2019-12666 in IOS XE
Summary
by MITRE
A vulnerability in the Guest Shell of Cisco IOS XE Software could allow an authenticated, local attacker to perform directory traversal on the base Linux operating system of Cisco IOS XE Software. The vulnerability is due to incomplete validation of certain commands. An attacker could exploit this vulnerability by first accessing the Guest Shell and then entering specific commands. A successful exploit could allow the attacker to execute arbitrary code on the base Linux operating system.
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Analysis
by VulDB Data Team • 12/28/2023
The vulnerability identified as CVE-2019-12666 resides within the Guest Shell component of Cisco IOS XE Software, representing a critical security weakness that undermines the operational integrity of network infrastructure devices. This flaw manifests as an incomplete validation mechanism for specific commands, creating an exploitable pathway for authenticated local attackers to escalate their privileges and gain unauthorized access to the underlying Linux operating system. The Guest Shell functionality, designed to provide users with a controlled environment for executing Linux commands, becomes a vector for privilege escalation when proper input sanitization fails to prevent malicious command sequences.
The technical exploitation of this vulnerability requires an authenticated attacker with local access to the device, leveraging the Guest Shell environment as an initial foothold. Attackers can manipulate command inputs to bypass validation checks and execute directory traversal operations that would normally be restricted. This incomplete validation creates a pathway for arbitrary code execution within the base Linux operating system, effectively allowing the attacker to operate with elevated privileges beyond the intended Guest Shell limitations. The vulnerability specifically targets the command processing logic within the Guest Shell, where certain input sequences are not properly sanitized or validated before being processed.
From an operational impact perspective, this vulnerability presents a significant risk to network security infrastructure, as it allows attackers to potentially compromise the entire device through privilege escalation. Once exploited, the attacker gains access to the underlying Linux operating system, which may contain sensitive configuration data, user credentials, or other critical system information. The vulnerability affects Cisco IOS XE Software versions that implement the Guest Shell functionality, potentially impacting a wide range of network devices including routers and switches that utilize this operating system. The local authentication requirement reduces the attack surface compared to remote exploits but still represents a serious concern for environments where physical or administrative access is possible.
Security mitigations for CVE-2019-12666 should prioritize immediate implementation of Cisco's official security patches and updates to address the command validation flaw. Network administrators should implement strict access controls and monitor Guest Shell usage to detect anomalous command patterns that might indicate exploitation attempts. The vulnerability aligns with CWE-22 directory traversal weakness and can be categorized under ATT&CK technique T1059.004 for command and scripting interpreter. Organizations should conduct comprehensive vulnerability assessments to identify affected devices and establish monitoring procedures for unauthorized Guest Shell access. Additionally, implementing network segmentation and privilege separation measures can help limit the potential impact if exploitation occurs, while regular security audits should verify that proper input validation mechanisms are in place to prevent similar vulnerabilities in other components of the system.