CVE-2015-6392 in NX-OS
Summary
by MITRE
Cisco NX-OS 4.1 through 7.2 on Nexus 2000, 5000, 5500, 5600, 6000, 7000, 7700, and 9000 devices allows remote attackers to cause a denial of service (device crash) via crafted IPv4 DHCP packets to the (1) DHCPv4 relay agent or (2) smart relay agent, aka Bug IDs CSCuq24603, CSCur93159, CSCus21693, and CSCut76171.
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Analysis
by VulDB Data Team • 09/22/2022
Cisco NX-OS software versions 4.1 through 7.2 contain a critical vulnerability in the DHCPv4 relay agent and smart relay agent implementations that enables remote attackers to trigger device crashes through carefully crafted IPv4 DHCP packets. This vulnerability affects multiple Nexus device families including 2000, 5000, 5500, 5600, 6000, 7000, 7700, and 9000 series switches, making it a widespread concern across Cisco's data center and enterprise networking infrastructure. The flaw manifests when the affected software components process malformed DHCP packets that contain specially constructed options or packet structures designed to exploit memory handling deficiencies within the DHCP relay agent implementations.
The technical nature of this vulnerability stems from insufficient input validation and memory management within the DHCP processing code paths. When the DHCPv4 relay agent or smart relay agent receives packets containing malformed DHCP options or unexpected packet structures, the software fails to properly sanitize these inputs before processing them. This leads to buffer overflows or memory corruption conditions that ultimately result in the device crashing and requiring manual reboot to restore normal operations. The vulnerability specifically targets the packet parsing logic that handles DHCP relay functionality, which is critical for network infrastructure devices that must forward DHCP requests between clients and servers across different network segments.
The operational impact of this vulnerability extends beyond simple service disruption to encompass significant network reliability concerns for organizations relying on Cisco Nexus switches. A successful exploitation can result in complete denial of service for the affected switch ports, potentially disrupting network connectivity for multiple devices depending on the scope of the DHCP relay functionality being utilized. Network administrators may experience unexpected downtime, especially in environments where DHCP is heavily relied upon for device provisioning and network access management. The vulnerability's remote exploitability means that attackers can trigger these crashes from external network positions without requiring physical access or local network privileges, making it particularly dangerous for publicly exposed network infrastructure.
Organizations should implement immediate mitigations including network segmentation to isolate vulnerable devices from untrusted networks, enabling DHCP snooping features to filter malformed packets, and applying the latest Cisco security patches that address the specific memory handling flaws in the DHCP relay agent implementations. The vulnerability aligns with CWE-121, heap-based buffer overflow, and CWE-125, out-of-bounds read, as the root causes involve improper memory management during packet processing. From an ATT&CK perspective, this vulnerability maps to T1499.004, Network Denial of Service, and T1595.001, Network Configuration, as it enables attackers to compromise network availability and potentially gain insights into network infrastructure configurations through service disruption attempts. Network monitoring should be enhanced to detect unusual DHCP packet patterns that may indicate exploitation attempts, and incident response procedures should be updated to address the rapid recovery requirements following device crashes.