CVE-2020-3407 in IOS XE
Summary
by MITRE
A vulnerability in the RESTCONF and NETCONF-YANG access control list (ACL) function of Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause the device to reload. The vulnerability is due to incorrect processing of the ACL that is tied to the RESTCONF or NETCONF-YANG feature. An attacker could exploit this vulnerability by accessing the device using RESTCONF or NETCONF-YANG. A successful exploit could allow an attacker to cause the device to reload, resulting in a denial of service (DoS) condition.
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Analysis
by VulDB Data Team • 09/25/2020
This vulnerability resides within the access control list implementation of Cisco IOS XE Software's RESTCONF and NETCONF-YANG interfaces, representing a critical flaw in the network device's authentication and authorization mechanisms. The issue stems from improper handling of access control lists that govern these management protocols, creating a pathway for unauthenticated remote exploitation. The vulnerability specifically affects devices running Cisco IOS XE Software where RESTCONF or NETCONF-YANG services are enabled, making it particularly dangerous in enterprise environments where these management protocols are commonly deployed for network automation and configuration management.
The technical flaw manifests through incorrect processing of access control lists that are associated with RESTCONF or NETCONF-YANG functionality, as categorized under CWE-284 Access Control. When an attacker constructs malicious requests to these interfaces, the system fails to properly validate the access control parameters, leading to a condition where unauthorized access can trigger system instability. This improper validation occurs during the ACL processing phase, where the device does not adequately check the legitimacy of access control entries, allowing malformed or crafted requests to bypass normal security checks. The vulnerability is particularly concerning because it requires no authentication credentials to exploit, making it an attractive target for automated attacks.
The operational impact of this vulnerability extends beyond simple denial of service, as a successful exploitation can result in complete device reloads that disrupt network services and potentially expose the network to further attacks. Network administrators may experience unexpected downtime as devices restart, potentially causing cascading failures in network infrastructure that depends on these management protocols. The DoS condition affects not just the immediate device but can impact broader network operations, especially in environments where multiple devices are managed through centralized RESTCONF or NETCONF-YANG interfaces. According to ATT&CK framework, this vulnerability maps to T1499.004 Network Denial of Service, where the attacker leverages legitimate management protocols to cause system disruption.
Mitigation strategies for this vulnerability should prioritize immediate patch deployment through official Cisco security advisories, as the flaw affects core network infrastructure components. Network administrators should disable RESTCONF and NETCONF-YANG services on affected devices until patches are applied, particularly in environments where these features are not actively required. Additional protective measures include implementing network segmentation to isolate management planes from production networks, deploying intrusion detection systems to monitor for suspicious access patterns, and establishing robust monitoring procedures to detect device reloads that may indicate exploitation attempts. The vulnerability demonstrates the critical importance of proper access control implementation in network management protocols, as highlighted by the NIST Cybersecurity Framework's Core Functions, particularly Protect and Detect. Organizations should also conduct thorough vulnerability assessments to identify all instances of affected Cisco IOS XE Software versions and ensure that all management interfaces are properly secured against unauthorized access attempts.