CVE-2019-1758 in IOS
Summary
by MITRE
A vulnerability in 802.1x function of Cisco IOS Software on the Catalyst 6500 Series Switches could allow an unauthenticated, adjacent attacker to access the network prior to authentication. The vulnerability is due to how the 802.1x packets are handled in the process path. An attacker could exploit this vulnerability by attempting to connect to the network on an 802.1x configured port. A successful exploit could allow the attacker to intermittently obtain access to the network.
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Analysis
by VulDB Data Team • 08/17/2023
The vulnerability identified as CVE-2019-1758 represents a critical weakness in the 802.1x authentication implementation within Cisco IOS Software running on Catalyst 6500 Series Switches. This flaw exists in the network access control mechanisms that are designed to prevent unauthorized devices from accessing network resources until proper authentication occurs. The vulnerability specifically impacts the handling of 802.1x packets during the authentication process, creating a window of opportunity for malicious actors to bypass the intended security controls. The attack vector requires physical proximity to the affected network port, making it an adjacent threat that operates within the local network segment where the switch is deployed. This type of vulnerability directly undermines the fundamental security principle of network segmentation and access control that 802.1x protocols are designed to enforce.
The technical exploitation of this vulnerability stems from improper packet handling within the 802.1x process path of the switch software. When an 802.1x configured port receives authentication requests, the software fails to properly validate or process incoming 802.1x packets, creating intermittent access opportunities for unauthorized network entry. This flaw manifests as a race condition or state management issue where the switch does not maintain consistent authentication states during the handshaking process. The vulnerability allows an attacker to establish network connectivity without completing the required authentication sequence, effectively enabling unauthorized access to the network segment. This behavior occurs because the switch's 802.1x implementation does not properly enforce the authentication state transitions that should prevent network access until valid credentials are presented. The intermittent nature of the vulnerability suggests that it may depend on specific timing conditions or packet sequencing that can be manipulated by an attacker.
The operational impact of CVE-2019-1758 is significant for organizations relying on 802.1x security controls for network access management. An attacker who successfully exploits this vulnerability can gain unauthorized access to network resources that would normally be restricted to authenticated users, potentially leading to data breaches, network reconnaissance, or lateral movement within the affected network. The vulnerability undermines the trust model that network administrators rely on when implementing 802.1x authentication, as it allows unauthorized access to occur without detection. This creates a persistent security risk where unauthorized devices can establish network presence and potentially remain undetected for extended periods. The intermittent nature of the exploitation means that the vulnerability may not be immediately apparent during routine network monitoring, making detection more challenging. Organizations may experience unauthorized network access without realizing the compromise has occurred, leading to potential data exfiltration or malicious activity within their network infrastructure.
The security implications of this vulnerability extend beyond simple unauthorized access, as it represents a failure in the core network access control mechanisms. This weakness aligns with CWE-284, which describes improper access control vulnerabilities, and could be categorized under ATT&CK technique T1078 for Valid Accounts and T1566 for Phishing. Organizations should implement immediate mitigations including applying the relevant Cisco security patches and updates to address the software flaw. Network segmentation strategies should be enhanced to limit the scope of potential compromise, and additional monitoring should be deployed to detect anomalous network access patterns. The vulnerability also highlights the importance of maintaining up-to-date network device firmware and conducting regular security assessments of network infrastructure. Network administrators should consider implementing additional authentication layers and access controls beyond 802.1x to provide defense-in-depth. The incident underscores the necessity of proper network access control implementation and the critical role that vendor security updates play in maintaining network security posture. Organizations should also review their network access control policies and ensure that multiple authentication mechanisms are in place to protect against similar vulnerabilities in other network components.