CVE-2018-15371 in IOS XE
Summary
by MITRE
A vulnerability in the shell access request mechanism of Cisco IOS XE Software could allow an authenticated, local attacker to bypass authentication and gain unrestricted access to the root shell of an affected device. The vulnerability exists because the affected software has insufficient authentication mechanisms for certain commands. An attacker could exploit this vulnerability by requesting access to the root shell of an affected device, after the shell access feature has been enabled. A successful exploit could allow the attacker to bypass authentication and gain unrestricted access to the root shell of the affected device.
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Analysis
by VulDB Data Team • 03/30/2020
The vulnerability identified as CVE-2018-15371 represents a critical authentication bypass flaw within Cisco IOS XE Software that fundamentally compromises the security posture of affected network devices. This weakness resides in the shell access request mechanism, where the software fails to implement adequate authentication controls for specific administrative commands. The vulnerability specifically affects devices where shell access has been enabled, creating a dangerous attack vector that allows authenticated local users to escalate their privileges without proper authorization. The flaw essentially undermines the principle of least privilege by permitting unauthorized access to the root shell, which contains the highest level of administrative control over the device's operations and configuration.
From a technical perspective, this vulnerability stems from insufficient authentication mechanisms that should have validated the legitimacy of shell access requests before granting elevated privileges. The attack requires an authenticated local user who already possesses some level of access to the device, but this initial access point becomes a critical weakness when combined with the flawed shell access control. The vulnerability operates at the command execution level where certain administrative functions fail to properly validate user credentials or session authenticity. This type of flaw aligns with CWE-287, which addresses improper authentication issues, and represents a classic case of privilege escalation through inadequate access controls. The software's failure to properly enforce authentication boundaries creates a pathway for attackers to bypass normal security measures that would typically prevent unauthorized root access.
The operational impact of this vulnerability extends far beyond simple privilege escalation, as it provides attackers with complete administrative control over affected network infrastructure. Once an attacker gains root shell access, they can modify device configurations, install malicious software, redirect traffic, or even disable security features entirely. This level of access enables comprehensive network compromise and can facilitate further attacks against other systems within the network perimeter. The vulnerability particularly affects enterprise networks where Cisco IOS XE devices serve as critical infrastructure components, making the potential damage substantial. Network administrators face the challenge of maintaining device integrity while dealing with the possibility that attackers could leverage this flaw to establish persistent access points within their network infrastructure.
Mitigation strategies for CVE-2018-15371 should focus on immediate remediation through official Cisco patches and updates, which address the underlying authentication bypass mechanism. Network administrators must ensure that shell access features are disabled unless absolutely necessary for legitimate administrative purposes, as this reduces the attack surface significantly. Implementation of network segmentation and monitoring solutions can help detect anomalous access patterns that might indicate exploitation attempts. Regular security audits should verify that only authorized personnel have access to devices with shell access enabled, and that proper access control lists are in place. The vulnerability also highlights the importance of following security best practices such as disabling unnecessary services, implementing strong authentication mechanisms, and maintaining comprehensive logging of administrative activities. Organizations should also consider implementing the principle of least privilege more rigorously, ensuring that administrative access is granted only when necessary and that access is regularly reviewed and audited. This vulnerability serves as a reminder of the critical importance of proper authentication controls in network infrastructure software and demonstrates how seemingly small flaws can lead to complete system compromise.