CVE-2017-6664 in IOS
Summary
by MITRE
A vulnerability in the Autonomic Networking feature of Cisco IOS XE Software could allow an unauthenticated, remote, autonomic node to access the Autonomic Networking infrastructure of an affected system, after the certificate for the autonomic node has been revoked. This vulnerability affected devices that are running Release 16.x of Cisco IOS XE Software and are configured to use Autonomic Networking. This vulnerability does not affect devices that are running an earlier release of Cisco IOS XE Software or devices that are not configured to use Autonomic Networking. More Information: CSCvd22328. Known Affected Releases: 15.5(1)S3.1 Denali-16.2.1.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 01/06/2021
The vulnerability identified as CVE-2017-6664 represents a critical security flaw within Cisco IOS XE Software's Autonomic Networking implementation that undermines the fundamental security assumptions of the autonomic network architecture. This weakness specifically targets the certificate validation mechanisms employed by autonomic nodes, creating a scenario where revoked certificates can still be accepted by the system, thereby allowing unauthorized access to the autonomic networking infrastructure. The flaw exists in devices running Cisco IOS XE Software releases 15.5(1)S3.1 Denali through 16.2.1, making it particularly concerning given the widespread deployment of these software versions across enterprise networks. The vulnerability demonstrates a failure in the certificate lifecycle management process, where the system does not properly enforce certificate revocation checks, creating a persistent security risk that can be exploited by malicious actors without requiring authentication credentials.
The technical implementation of this vulnerability stems from inadequate certificate validation logic within the autonomic networking subsystem of the IOS XE software stack. When an autonomic node attempts to establish communication with the autonomic network infrastructure, the system should verify that the node's certificate has not been revoked through the Certificate Revocation List (CRL) or Online Certificate Status Protocol (OCSP) mechanisms. However, the flaw allows the system to accept connections from nodes presenting revoked certificates, effectively bypassing the intended security controls. This behavior violates the core principles of public key infrastructure (PKI) management and represents a failure in the certificate validation process that aligns with CWE-295, which addresses improper certificate validation. The vulnerability's impact is particularly severe because it operates at the network infrastructure level, potentially allowing attackers to gain unauthorized access to sensitive network management functions and data that should be restricted to legitimate autonomic nodes.
Operational implications of CVE-2017-6664 extend beyond simple unauthorized access, as it fundamentally compromises the trust model that autonomic networking relies upon for secure device authentication and communication. An attacker exploiting this vulnerability could potentially establish persistent access to the autonomic network infrastructure, enabling them to monitor network traffic, modify device configurations, or even escalate privileges within the network management system. The vulnerability's remote nature means that attackers can exploit it without physical access to the network equipment, making it particularly dangerous in environments where network devices are exposed to untrusted networks. This weakness directly relates to ATT&CK technique T1566, which covers credential harvesting and network infiltration through compromised authentication mechanisms. The attack surface is further expanded by the fact that the vulnerability affects devices configured for autonomic networking, which typically operate with elevated privileges and access to critical network functions, potentially allowing lateral movement and privilege escalation throughout the network infrastructure.
Mitigation strategies for CVE-2017-6664 require immediate implementation of software updates to affected Cisco IOS XE releases, as the vulnerability is addressed through patches that properly enforce certificate revocation checks within the autonomic networking subsystem. Organizations should prioritize updating their network infrastructure to the latest available software versions that contain the necessary security fixes, particularly focusing on devices running releases 15.5(1)S3.1 through 16.2.1. Network administrators should also implement additional monitoring controls to detect anomalous behavior from autonomic nodes that might indicate exploitation attempts, including monitoring for unauthorized certificate usage patterns and unusual network access requests. The vulnerability highlights the importance of proper certificate lifecycle management and the need for robust certificate validation mechanisms within network infrastructure software. Organizations should review their autonomic networking configurations and consider disabling the feature entirely if it is not critical to their operations, as this provides an immediate defense against exploitation. Additionally, implementing network segmentation and access controls around autonomic networking infrastructure can help limit the potential impact if the vulnerability is exploited, while maintaining proper audit trails to detect any unauthorized access attempts that might occur despite the security controls.