CVE-2019-1599 in NX-OS
Summary
by MITRE
A vulnerability in the network stack of Cisco NX-OS Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on the affected device. The vulnerability is due to an issue with allocating and freeing memory buffers in the network stack. An attacker could exploit this vulnerability by sending crafted TCP streams to an affected device in a sustained way. A successful exploit could cause the network stack of an affected device to run out of available buffers, impairing operations of control plane and management plane protocols, resulting in a DoS condition. Note: This vulnerability can be triggered only by traffic that is destined to an affected device and cannot be exploited using traffic that transits an affected device. Nexus 1000V Switch for Microsoft Hyper-V is affected in versions prior to 5.2(1)SM3(2.1). Nexus 1000V Switch for VMware vSphere is affected in versions prior to 5.2(1)SV3(4.1a). Nexus 3000 Series Switches are affected in versions prior to 7.0(3)I7(6) and 9.2(2). Nexus 3500 Platform Switches are affected in versions prior to 6.0(2)A8(11), 7.0(3)I7(6), and 9.2(2). Nexus 3600 Platform Switches are affected in versions prior to 7.0(3)F3(5) and 9.2(2). Nexus 5500, 5600, and 6000 Series Switches are affected in versions prior to 7.1(5)N1(1b) and 7.3(5)N1(1). Nexus 7000 and 7700 Series Switches are affected in versions prior to 6.2(22. Nexus 9500 R-Series Line Cards and Fabric Modules are affected in versions prior to 7.0(3)F3(5) and 9.2(2). UCS 6200 and 6300 Series Fabric Interconnect are affected in versions prior to 3.2(3j) and 4.0(2a). UCS 6400 Series Fabric Interconnect are affected in versions prior to 4.0(2a).
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Analysis
by VulDB Data Team • 07/29/2023
This vulnerability resides within the network stack implementation of Cisco NX-OS Software, specifically manifesting as a memory management flaw that enables unauthorized remote attackers to induce denial of service conditions. The core technical issue stems from improper handling of memory buffer allocation and deallocation processes within the network processing pipeline. According to CWE-129, this represents a weakness in input validation that allows for memory corruption through improper buffer handling. The vulnerability operates at the protocol level where TCP stream processing occurs, making it particularly dangerous as it can be exploited without authentication requirements, aligning with ATT&CK technique T1498.100 for network denial of service attacks.
The exploitation mechanism involves sending sustained, crafted TCP streams directly to the vulnerable device, targeting the specific memory allocation routines within the network stack. This attack vector operates exclusively against traffic destined for the affected device rather than traffic passing through it, which limits the scope but maintains significant impact. The memory buffer exhaustion occurs when the network stack continuously allocates new buffers without properly freeing previously used ones, leading to a gradual depletion of available resources. This memory management failure creates a cascading effect that impacts not only data plane operations but also critical control plane and management plane protocols, as noted in the vulnerability description.
The operational impact of this vulnerability extends beyond simple service interruption, as it affects the fundamental network infrastructure capabilities. When memory buffers are exhausted, the device cannot properly process incoming packets or maintain established connections, resulting in complete service disruption. Control plane protocols such as routing updates, management communications, and other critical network functions become impaired, potentially leading to network partitions or complete loss of network visibility. This aligns with ATT&CK tactic TA0043 for resource exhaustion and demonstrates how memory management flaws can create systemic network failures rather than isolated incidents.
Mitigation strategies should focus on implementing immediate software updates to patched versions across all affected Cisco NX-OS platforms, including Nexus switches, UCS fabric interconnects, and virtual switch implementations. Network administrators should also consider implementing rate limiting and traffic filtering mechanisms at network boundaries to reduce the impact of potential exploitation attempts. The vulnerability's nature as a memory management issue suggests that monitoring buffer usage patterns and implementing automated alerts for unusual memory consumption could provide early detection capabilities. Additionally, network segmentation and access control measures should be reviewed to limit potential attack surfaces, particularly for devices running vulnerable software versions as specified in the affected product list.