CVE-2006-0485 in IOS
Summary
by MITRE
The TCL shell in Cisco IOS 12.2(14)S before 12.2(14)S16, 12.2(18)S before 12.2(18)S11, and certain other releases before 25 January 2006 does not perform Authentication, Authorization, and Accounting (AAA) command authorization checks, which may allow local users to execute IOS EXEC commands that were prohibited via the AAA configuration, aka Bug ID CSCeh73049.
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Analysis
by VulDB Data Team • 03/12/2021
The vulnerability described in CVE-2006-0485 represents a critical authorization flaw within Cisco IOS software that affects multiple release versions including 12.2(14)S through 12.2(14)S15 and 12.2(18)S through 12.2(18)S10. This issue specifically impacts the Tcl shell implementation within Cisco IOS operating systems, creating a significant security gap that allows local users to bypass configured AAA command authorization restrictions. The flaw stems from the absence of proper AAA authorization checks within the Tcl shell environment, which is a component designed to provide scripting capabilities for network device management and automation. This vulnerability was particularly concerning because it directly undermined the security controls that network administrators relied upon to restrict user access to specific IOS EXEC commands. The issue was officially documented under Bug ID CSCeh73049 and was addressed through Cisco security patches released on or before 25 January 2006, demonstrating the urgency with which this authorization bypass was treated by the vendor.
The technical nature of this vulnerability places it within the scope of CWE-284, which describes improper access control mechanisms, and specifically relates to the failure of implementing proper authorization checks in a privileged execution environment. The flaw operates by allowing local users who can access the Tcl shell to execute IOS EXEC commands that would normally be restricted based on AAA configuration settings. This occurs because the Tcl shell does not perform the same authorization validation that occurs in the standard IOS EXEC mode, creating a vector for privilege escalation and unauthorized command execution. The vulnerability essentially creates a backdoor within the normal command authorization flow, where users can circumvent the normal AAA authorization process that should validate whether a particular user has permission to execute specific commands. This bypass mechanism operates at the command execution level rather than at authentication, making it particularly dangerous as it allows users who have already gained local access to escalate their privileges further within the network device.
The operational impact of CVE-2006-0485 extends beyond simple command execution, as it enables potential attackers to gain unauthorized access to sensitive network device functions and configurations. Local users who can access the Tcl shell environment can execute commands that may include system-level operations such as configuration changes, interface modifications, or access to sensitive data that should be restricted to authorized administrative personnel. This vulnerability directly affects the principle of least privilege that network administrators implement through AAA configurations, potentially allowing attackers to discover and exploit other security weaknesses within the network infrastructure. The impact is particularly severe in enterprise environments where network devices are configured with specific command authorizations to limit administrative access and prevent accidental or malicious configuration changes. The vulnerability also aligns with ATT&CK technique T1068, which involves the use of existing valid accounts to gain access to systems, as local access to the Tcl shell environment is typically required to exploit this flaw.
Mitigation strategies for CVE-2006-0485 primarily focus on implementing the security patches released by Cisco to address the specific authorization bypass in the Tcl shell component. Network administrators should immediately update affected Cisco IOS devices to versions 12.2(14)S16, 12.2(18)S11, or later releases that contain the necessary fixes for the AAA authorization checks. Additionally, organizations should implement network segmentation and access control measures to limit local access to network devices, particularly to reduce the attack surface for users who might attempt to exploit this vulnerability. The configuration of AAA policies should be reviewed to ensure that command authorization restrictions are properly enforced across all execution environments within the IOS system. Network monitoring should be enhanced to detect unauthorized command execution patterns that might indicate exploitation attempts. This vulnerability also underscores the importance of maintaining up-to-date security patches and implementing comprehensive security monitoring solutions that can detect anomalous behavior within network device management interfaces. Organizations should consider implementing additional logging and audit controls to track command execution within the Tcl shell environment and other privileged execution contexts to detect potential exploitation attempts.