CVE-2019-1759 in IOS XE
Summary
by MITRE
A vulnerability in access control list (ACL) functionality of the Gigabit Ethernet Management interface of Cisco IOS XE Software could allow an unauthenticated, remote attacker to reach the configured IP addresses on the Gigabit Ethernet Management interface. The vulnerability is due to a logic error that was introduced in the Cisco IOS XE Software 16.1.1 Release, which prevents the ACL from working when applied against the management interface. An attacker could exploit this issue by attempting to access the device via the management interface.
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Analysis
by VulDB Data Team • 08/17/2023
The vulnerability identified as CVE-2019-1759 represents a critical access control flaw within Cisco IOS XE Software that affects the Gigabit Ethernet Management interface. This issue stems from a logic error introduced in the 16.1.1 release of the software, fundamentally undermining the intended security controls that should protect management access to network devices. The vulnerability specifically targets the access control list functionality, which serves as a critical defense mechanism for restricting unauthorized network access to management interfaces. When ACLs are properly configured and applied to management interfaces, they should prevent unauthorized access attempts by filtering incoming traffic based on predefined rules and IP address restrictions.
The technical implementation of this flaw involves a logical error in how the software processes access control lists when applied to management interfaces, causing the ACLs to become ineffective or completely bypassed. This logic error essentially creates a security bypass condition where even properly configured access control rules fail to enforce their intended restrictions. Attackers can exploit this vulnerability by simply attempting to access the management interface without authentication, as the ACL functionality that should normally prevent such access becomes non-operational. The vulnerability is particularly concerning because it affects the core management interface of network devices, which typically provides administrators with critical access to device configuration and operational controls.
The operational impact of CVE-2019-1759 extends beyond simple unauthorized access, as it provides attackers with potential pathways to compromise entire network infrastructures through management interface exploitation. This vulnerability enables remote attackers to reach configured IP addresses on the management interface without authentication, potentially allowing for complete device compromise, configuration modification, or data exfiltration. The implications are especially severe for network administrators who rely on management interfaces for device monitoring and control, as this vulnerability essentially removes a fundamental security boundary. According to CWE classification, this vulnerability maps to CWE-284 Access Control Bypass, which specifically addresses scenarios where access controls are improperly enforced or bypassed.
From an adversarial perspective, this vulnerability aligns with ATT&CK framework technique T1078 Valid Accounts, as attackers can leverage the bypassed access controls to gain unauthorized access to management interfaces without requiring legitimate credentials. The vulnerability also intersects with T1059 Command and Scripting Interpreter, as successful exploitation could enable attackers to execute commands on compromised devices. Network security professionals must consider this vulnerability as part of a broader attack surface assessment, particularly when evaluating management interface security controls. The risk is amplified by the fact that many organizations rely heavily on management interfaces for routine operations, making this vulnerability particularly attractive to threat actors seeking persistent access to network infrastructure.
Mitigation strategies for CVE-2019-1759 primarily focus on immediate software updates and configuration adjustments to restore proper access control functionality. Cisco has released software updates that address the logic error in the ACL implementation, and organizations should prioritize applying these patches to all affected devices. Additionally, network administrators should implement additional layers of security controls such as network segmentation, restricted management interface access, and enhanced monitoring of management interface traffic. The vulnerability highlights the importance of thorough regression testing during software releases, as logic errors in security-critical components can have severe operational consequences. Organizations should also consider implementing network access control lists at multiple levels of their network architecture to provide defense-in-depth against similar vulnerabilities that might not be immediately patched or addressed.