DoS via UDP/TCP Flood in Cisco NX-OS
CVE-2026-20173 Published on October 7, 2026
Cisco NX-OS Software Denial of Service Vulnerability
A vulnerability in Cisco NX-OS Software could allow an unauthenticated, remote attacker to exhaust system resources, causing a denial of service (DoS) condition.
This vulnerability exists because rate limiting was improperly applied to some protocols. An attacker could exploit this vulnerability by sending a high rate of UDP or TCP connections to a data plane interface on an affected device. A successful exploit could allow the attacker to cause instability to various routing and control plane protocols through some packet loss and temporary disruptions, causing a DoS condition. This DoS condition will clear without manual intervention soon after the high rate of traffic is stopped.
Vulnerability Analysis
CVE-2026-20173 can be exploited with network access, and does not require authorization privileges or user interaction. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality and integrity, and a small impact on availability.
Weakness Type
Allocation of Resources Without Limits or Throttling
The software allocates a reusable resource or group of resources on behalf of an actor without imposing any restrictions on the size or number of resources that can be allocated, in violation of the intended security policy for that actor.
Products Associated with CVE-2026-20173
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Affected Versions
Cisco NX-OS Software:- Version 8.2(5) is affected.
- Version 7.3(5)D1(1) is affected.
- Version 8.4(2) is affected.
- Version 8.4(3) is affected.
- Version 9.2(3) is affected.
- Version 9.2(2v) is affected.
- Version 7.3(4)D1(1) is affected.
- Version 8.2(1) is affected.
- Version 9.2(1) is affected.
- Version 9.2(2t) is affected.
- Version 9.2(3y) is affected.
- Version 9.3(2) is affected.
- Version 8.1(1) is affected.
- Version 8.2(2) is affected.
- Version 8.3(2) is affected.
- Version 7.3(2)D1(3a) is affected.
- Version 9.2(4) is affected.
- Version 8.1(2) is affected.
- Version 7.3(3)D1(1) is affected.
- Version 8.2(3) is affected.
- Version 8.4(1) is affected.
- Version 7.3(0)DX(1) is affected.
- Version 7.3(2)D1(1) is affected.
- Version 9.3(1) is affected.
- Version 7.3(2)D1(2) is affected.
- Version 8.2(4) is affected.
- Version 9.3(1z) is affected.
- Version 9.2(2) is affected.
- Version 8.1(2a) is affected.
- Version 7.3(2)D1(3) is affected.
- Version 8.3(1) is affected.
- Version 7.3(1)D1(1) is affected.
- Version 7.3(0)D1(1) is affected.
- Version 9.3(3) is affected.
- Version 7.3(2)D1(1d) is affected.
- Version 9.3(4) is affected.
- Version 7.3(6)D1(1) is affected.
- Version 8.2(6) is affected.
- Version 9.3(5) is affected.
- Version 9.3(6) is affected.
- Version 8.4(4) is affected.
- Version 7.3(7)D1(1) is affected.
- Version 9.3(5w) is affected.
- Version 8.2(7) is affected.
- Version 9.3(7) is affected.
- Version 9.3(7k) is affected.
- Version 7.3(8)D1(1) is affected.
- Version 9.3(7a) is affected.
- Version 8.2(7a) is affected.
- Version 9.3(8) is affected.
- Version 8.4(4a) is affected.
- Version 8.4(5) is affected.
- Version 8.2(8) is affected.
- Version 9.3(9) is affected.
- Version 7.3(9)D1(1) is affected.
- Version 8.4(6) is affected.
- Version 9.3(10) is affected.
- Version 8.2(9) is affected.
- Version 10.3(1) is affected.
- Version 8.4(7) is affected.
- Version 10.3(2) is affected.
- Version 8.4(6a) is affected.
- Version 9.3(11) is affected.
- Version 10.3(3) is affected.
- Version 8.2(10) is affected.
- Version 9.3(12) is affected.
- Version 10.4(1) is affected.
- Version 8.4(8) is affected.
- Version 10.3(99w) is affected.
- Version 10.3(3w) is affected.
- Version 10.3(99x) is affected.
- Version 10.3(3o) is affected.
- Version 8.4(9) is affected.
- Version 10.3(4) is affected.
- Version 10.3(3p) is affected.
- Version 10.3(4a) is affected.
- Version 10.4(2) is affected.
- Version 10.3(3q) is affected.
- Version 9.3(13) is affected.
- Version 8.2(11) is affected.
- Version 10.3(5) is affected.
- Version 10.4(3) is affected.
- Version 10.3(3x) is affected.
- Version 10.3(4g) is affected.
- Version 10.5(1) is affected.
- Version 8.4(10) is affected.
- Version 10.3(3r) is affected.
- Version 10.3(6) is affected.
- Version 9.3(14) is affected.
- Version 10.4(4) is affected.
- Version 10.3(4h) is affected.
- Version 10.5(2) is affected.
- Version 8.4(11) is affected.
- Version 10.3(7) is affected.
- Version 10.4(5) is affected.
- Version 10.5(3) is affected.
- Version 9.3(15) is affected.
- Version 10.4(4g) is affected.
- Version 10.5(4) is affected.
- Version 8.4(12) is affected.
- Version 10.5(3t) is affected.
- Version 10.3(8) is affected.
- Version 10.4(6) is affected.
- Version 10.5(3s) is affected.
- Version 10.5(3e) is affected.
- Version 10.5(3o) is affected.
- Version 9.3(16) is affected.
- Version 10.5(3p) is affected.
- Version 10.4(7) is affected.
- Version 10.5(5) is affected.
- Version 9.3(17) is affected.