CVE-2016-6438 in IOS XE
Summary
by MITRE
A vulnerability in Cisco IOS XE Software running on Cisco cBR-8 Converged Broadband Routers could allow an unauthenticated, remote attacker to cause a configuration integrity change to the vty line configuration on an affected device. This vulnerability affects the following releases of Cisco IOS XE Software running on Cisco cBR-8 Converged Broadband Routers: All 3.16S releases, All 3.17S releases, Release 3.18.0S, Release 3.18.1S, Release 3.18.0SP. More Information: CSCuz62815. Known Affected Releases: 15.5(3)S2.9, 15.6(2)SP. Known Fixed Releases: 15.6(1.7)SP1, 16.4(0.183), 16.5(0.1).
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Analysis
by VulDB Data Team • 09/26/2022
The vulnerability identified as CVE-2016-6438 represents a significant security flaw in Cisco IOS XE Software affecting cBR-8 Converged Broadband Routers. This issue stems from insufficient authentication mechanisms within the router's vty line configuration management system, allowing unauthorized remote attackers to manipulate critical network access parameters without requiring valid credentials. The vulnerability specifically targets the virtual teletypewriter line configuration, which controls remote access sessions to the device, making it particularly dangerous for network administrators who rely on secure remote management capabilities. The flaw exists across multiple software releases including all 3.16S and 3.17S versions, as well as specific 3.18 releases, indicating a widespread impact across the affected product line.
The technical implementation of this vulnerability demonstrates a classic privilege escalation issue within network device management interfaces. Attackers can exploit this weakness to modify vty line configurations, potentially gaining unauthorized access to network devices or disrupting legitimate administrative sessions. The vulnerability's remote nature means that attackers do not require physical access or local network presence to exploit the flaw, making it particularly concerning for publicly accessible network infrastructure. This type of configuration integrity violation falls under the CWE-269: "Improper Privilege Management" category, where the system fails to properly enforce access controls for administrative functions. The attack vector requires no authentication credentials, which aligns with the ATT&CK technique T1078.004: "Valid Accounts: SSH" where attackers can leverage existing access mechanisms to manipulate system configurations.
The operational impact of this vulnerability extends beyond simple unauthorized access, as it can compromise the entire network management infrastructure. When an attacker successfully modifies vty line configurations, they can potentially disable legitimate administrative access, redirect management sessions, or establish persistent backdoor access points. This configuration manipulation capability creates a significant risk for network security posture, as it allows attackers to undermine the device's integrity and potentially escalate their privileges further within the network. The affected releases span multiple software versions, indicating that organizations running these specific IOS XE versions are at risk regardless of their exact patch level within the affected release series. The vulnerability's persistence across multiple service packs and release trains suggests that the underlying flaw was not adequately addressed through standard software updates.
Organizations should prioritize immediate remediation of affected devices by upgrading to the fixed software releases mentioned in the advisory, specifically versions 15.6(1.7)SP1, 16.4(0.183), and 16.5(0.1). Network administrators should also implement additional monitoring controls to detect unauthorized configuration changes, particularly focusing on vty line modifications that may indicate exploitation attempts. The vulnerability highlights the importance of maintaining current security patches and implementing network segmentation to limit the impact of such attacks. Organizations should also review their remote access policies and ensure that only authorized personnel have access to network management interfaces, while implementing multi-factor authentication where possible to add additional layers of security. The incident underscores the critical need for robust configuration management practices and continuous security monitoring to detect and respond to unauthorized modifications to network device configurations.