CVE-2007-4632 in IOS
Summary
by MITRE
Cisco IOS 12.2E, 12.2F, and 12.2S places a "no login" line into the VTY configuration when an administrator makes certain changes to a (1) VTY/AUX or (2) CONSOLE setting on a device without AAA enabled, which allows remote attackers to bypass authentication and obtain a terminal session, a different vulnerability than CVE-1999-0293 and CVE-2005-2105.
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Analysis
by VulDB Data Team • 07/25/2019
This vulnerability exists in Cisco IOS software versions 12.2E, 12.2F, and 12.2S where the configuration handling mechanism fails to properly manage authentication settings during VTY, AUX, or CONSOLE configuration changes. When administrators modify these terminal line settings on devices that do not have AAA (Authentication, Authorization, and Accounting) services enabled, the system automatically inserts a "no login" directive into the VTY configuration. This behavior creates an unexpected security loophole that allows unauthorized remote attackers to establish terminal sessions without proper authentication credentials.
The technical flaw stems from improper configuration management within the IOS operating system where the automatic insertion of the "no login" command effectively disables authentication requirements for remote terminal access. This vulnerability specifically affects devices running Cisco IOS software where AAA is not configured or enabled, making the system susceptible to exploitation through remote network access. The flaw operates at the configuration layer where the system fails to maintain proper authentication controls during routine administrative operations, creating a persistent backdoor mechanism that bypasses normal authentication procedures.
The operational impact of this vulnerability is significant as it provides attackers with unauthorized access to network devices through terminal sessions, potentially enabling further exploitation within the network infrastructure. An attacker who can establish a terminal session gains access to the device's command-line interface, which could lead to complete device compromise, data exfiltration, or disruption of network services. This vulnerability differs from previously identified issues such as CVE-1999-0293 and CVE-2005-2105, indicating a distinct code path or configuration handling mechanism that was not properly addressed in earlier security patches.
From a cybersecurity perspective, this vulnerability aligns with CWE-284 (Improper Access Control) and represents a privilege escalation vector that allows unauthenticated access to network device management interfaces. The ATT&CK framework categorizes this as a credential access technique where adversaries can bypass authentication mechanisms to gain access to system interfaces. The vulnerability demonstrates a classic configuration management flaw where automated system behavior creates unintended access paths that undermine security controls.
Organizations should implement immediate mitigations including enabling AAA services on affected devices, reviewing and validating terminal line configurations, and implementing proper access control lists to restrict remote access to management interfaces. Network administrators must ensure that all devices running vulnerable IOS versions have proper authentication mechanisms enabled and that configuration changes are carefully monitored to prevent automatic insertion of insecure settings. Regular security audits of device configurations should include verification that authentication requirements remain intact during administrative operations, and network segmentation should be implemented to limit the potential impact of successful exploitation attempts.