CVE-2018-0152 in IOS XE
Summary
by MITRE
A vulnerability in the web-based user interface (web UI) of Cisco IOS XE Software could allow an authenticated, remote attacker to gain elevated privileges on an affected device. The vulnerability exists because the affected software does not reset the privilege level for each web UI session. An attacker who has valid credentials for an affected device could exploit this vulnerability by remotely accessing a VTY line to the device. A successful exploit could allow the attacker to access an affected device with the privileges of the user who previously logged in to the web UI. This vulnerability affects Cisco devices that are running a vulnerable release of Cisco IOS XE Software, if the HTTP Server feature is enabled and authentication, authorization, and accounting (AAA) authorization is not configured for EXEC sessions. The default state of the HTTP Server feature is version-dependent. This vulnerability was introduced in Cisco IOS XE Software Release 16.1.1. Cisco Bug IDs: CSCvf71769.
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Analysis
by VulDB Data Team • 02/06/2021
The vulnerability described in CVE-2018-0152 represents a critical privilege escalation flaw within Cisco IOS XE Software's web-based user interface implementation. This security weakness specifically targets the authentication and authorization mechanisms that govern user access to network devices, creating a persistent security risk that can be exploited by authenticated attackers. The vulnerability stems from improper session management practices where the system fails to properly reset privilege levels between web UI sessions, allowing attackers to maintain elevated access rights across multiple connections. This flaw particularly affects devices running Cisco IOS XE Software versions 16.1.1 and later, where the HTTP Server feature is enabled and AAA authorization is not properly configured for EXEC sessions. The vulnerability's introduction in release 16.1.1 indicates a regression or design oversight that has persisted across subsequent versions, making it a significant concern for organizations maintaining legacy deployments.
The technical exploitation of this vulnerability requires an attacker to possess valid credentials for the target device, which provides a baseline level of access but does not immediately grant elevated privileges. The attacker must first establish a valid session through the web UI interface, after which the system's failure to properly reset privilege contexts allows the attacker to maintain elevated access rights. This occurs because the device's authentication system does not properly enforce privilege boundaries between different session contexts, particularly when transitioning between web UI and VTY line access. The vulnerability specifically impacts the privilege management architecture by creating a persistent state where elevated privileges from one session can be carried forward to subsequent connections, effectively bypassing the normal authentication and authorization checks that should occur with each new session. This flaw operates at the intersection of authentication management and session handling, creating a security boundary violation that can be exploited by attackers who understand the system's privilege escalation mechanics.
The operational impact of this vulnerability extends beyond simple privilege escalation to potentially enable complete device compromise and unauthorized network access. An attacker who successfully exploits this vulnerability can essentially maintain persistent access to the target device with elevated privileges, allowing them to modify configurations, access sensitive data, or establish backdoors for continued unauthorized access. The vulnerability's effect is particularly concerning because it can be exploited remotely without requiring physical access to the device, making it a significant threat in environments where network devices are accessible from external networks. Organizations running affected Cisco IOS XE Software versions face the risk of unauthorized access to critical network infrastructure, potentially leading to data breaches, network disruption, or complete compromise of their network security posture. The vulnerability affects a wide range of Cisco devices including routers and switches that support the HTTP Server feature, making it a broad security concern across multiple network segments and operational environments.
Organizations should implement immediate mitigations to address this vulnerability by ensuring proper AAA authorization configuration for EXEC sessions and disabling the HTTP Server feature on devices where it is not required. The recommended approach involves configuring AAA authorization for EXEC sessions to enforce proper privilege boundaries and ensuring that each new session starts with appropriate authentication checks. Network administrators should also consider disabling HTTP Server functionality on devices that do not require web-based management access, as this reduces the attack surface for exploitation. Additionally, organizations should implement network segmentation and access controls to limit the potential impact of successful exploitation, particularly by restricting access to management interfaces from trusted network segments only. Regular security audits and vulnerability assessments should be conducted to identify and remediate similar privilege escalation vulnerabilities across the network infrastructure. The vulnerability aligns with CWE-285, which addresses improper authorization issues, and maps to ATT&CK technique T1068, which covers local privilege escalation through session management flaws, highlighting the need for comprehensive security controls that address both authentication and authorization mechanisms within network device management interfaces.