CVE-2014-3341 in NX-OS
Summary
by MITRE
The SNMP module in Cisco NX-OS 7.0(3)N1(1) and earlier on Nexus 5000 and 6000 devices provides different error messages for invalid requests depending on whether the VLAN ID exists, which allows remote attackers to enumerate VLANs via a series of requests, aka Bug ID CSCup85616.
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Analysis
by VulDB Data Team • 02/10/2022
The vulnerability identified as CVE-2014-3341 affects the SNMP module within Cisco NX-OS software versions 7.0(3)N1(1) and earlier running on Nexus 5000 and 6000 series switches. This issue represents a classic information disclosure vulnerability that stems from inconsistent error handling within the network device's SNMP implementation. The flaw manifests when the system processes invalid SNMP requests, specifically those involving VLAN identifiers, where the response varies significantly based on whether the requested VLAN ID exists within the device's configuration. This differential response behavior creates a predictable pattern that malicious actors can exploit to systematically determine the existence of specific VLANs on the network infrastructure.
The technical mechanism behind this vulnerability involves the SNMP protocol's handling of invalid requests within the switch's network operating system. When an attacker sends SNMP requests with non-existent VLAN IDs, the system responds with error messages that contain different wording or structure compared to responses for valid but non-existent VLANs. This inconsistency provides attackers with a reliable method to distinguish between existing and non-existing VLANs through repeated probing attempts. The vulnerability specifically impacts the NX-OS software's SNMP implementation, which is critical for network management and monitoring operations, making it particularly dangerous in enterprise environments where VLAN segmentation is commonly used for security isolation.
From an operational impact perspective, this vulnerability enables remote attackers to perform VLAN enumeration attacks without requiring authentication or direct access to the network device. The ability to discover VLAN configurations undermines network security through the principle of least disclosure, potentially exposing sensitive network topology information to unauthorized parties. This intelligence gathering capability can significantly aid attackers in planning more sophisticated attacks, such as VLAN hopping attempts or targeted network reconnaissance that could lead to privilege escalation or lateral movement within the network infrastructure. The vulnerability affects Cisco Nexus 5000 and 6000 series switches, which are widely deployed in enterprise data centers and core network environments, amplifying the potential impact across multiple organizations.
The vulnerability aligns with CWE-200, which describes information exposure through error messages, and represents a clear violation of the principle of least privilege in network security. From an ATT&CK framework perspective, this issue maps to the reconnaissance phase, specifically T1046 network service scanning and T1082 system information discovery, where attackers can systematically map network topology and configuration details. The vulnerability also relates to T1590 threat actor reconnaissance and T1592 infrastructure reconnaissance, as it enables attackers to gather intelligence about network infrastructure without detection. Organizations should implement immediate mitigations including applying the relevant Cisco security patches, disabling unnecessary SNMP access, implementing proper access controls, and monitoring for suspicious SNMP traffic patterns that might indicate enumeration attempts.
Cisco addressed this vulnerability through software updates that standardized the error responses for invalid VLAN requests, eliminating the information leakage that enabled enumeration attacks. The fix ensures that all invalid requests receive consistent error responses regardless of the VLAN ID's existence, preventing attackers from distinguishing between valid and invalid VLAN references. Network administrators should also consider implementing SNMP access controls, limiting SNMP access to trusted management stations, and deploying network monitoring solutions that can detect and alert on suspicious SNMP enumeration patterns. The vulnerability demonstrates the importance of consistent error handling in security-critical systems and highlights how seemingly minor implementation details can create significant security weaknesses in network infrastructure devices. Organizations should review their network device configurations to ensure that SNMP services are properly secured and that unnecessary access is restricted to maintain the confidentiality of network topology information.