CVE-2021-1591

Cisco Nexus 9500 Series Switches Access Control List Bypass Vulnerability

MEDIUM

5.3

CVSS Score

Published: August 25, 2021 at 07:11 PM UTC

Updated: June 17, 2026 at 03:32 AM UTC

7 products affected across 1 vendorNx OSNexus 9508Nexus 9516

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Severity

MEDIUM5.3

Exploit prediction

EPSS 1.0%

SSVC

No known exploit

Description

A vulnerability in the EtherChannel port subscription logic of Cisco Nexus 9500 Series Switches could allow an unauthenticated, remote attacker to bypass access control list (ACL) rules that are configured on an affected device. This vulnerability is due to oversubscription of resources that occurs when applying ACLs to port channel interfaces. An attacker could exploit this vulnerability by attempting to access network resources that are protected by the ACL. A successful exploit could allow the attacker to access network resources that would be protected by the ACL that was applied on the port channel interface.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Nx OS · Cisconpm

95%

9.3(4)

cisco-nexus-9500-16-slot (environment) · cisco-nexus-9500-4-slot (environment) · cisco-nexus-9500-8-slot (environment) · cisco-nexus-9504 (environment) · cisco-nexus-9508 (environment) · cisco-nexus-9516 (environment)

Nexus 9500 16-Slot · Ciscodevice

80%

All versions

Nexus 9500 4-Slot · Ciscodevice

80%

All versions

Nexus 9500 8-Slot · Ciscodevice

80%

All versions

Nexus 9504 · Ciscodevice

80%

All versions