Advisory severityMedium5.8Cisco Updated

Medium [CVE-2026-20038] Cisco Nexus 9000 Series Fabric Switches in ACI Mode Endpoint Group Contract Bypass Vulnerability

This medium-severity Cisco advisory covers CVE-2026-20038 affecting NX-OS System Software in ACI Mode, Nexus 9000 Series Switches.

Aggregated and source-linked by VulniPulse. Data sources, validation and limitations.

cisco-sa-aci-epgcbp-SfDU7NLf Source published Oct 7, 2026Source updated Oct 7, 2026

VulniPulse record published Oct 7, 2026Record updated Oct 8, 2026

CVE-2026-20038

Affected products & platforms

CiscoSwitchesNexusNX-OSNexus 9000

Open source advisory

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Summary

A vulnerability in the endpoint group (EPG) contract functionality of Cisco Nexus 9000 Series Fabric Switches in ACI Mode could allow an unauthenticated, remote attacker to bypass configured EPG contracts.

This vulnerability is due to an improper control with EPG contracts. An attacker could exploit this vulnerability by sending IPv4 or IPv6 packets using UDP source and destination ports that are assigned to DHCP traffic through an affected device.

A successful exploit could allow the attacker to bypass EPG contracts on the affected device.

Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability.

This advisory is part of a group of advisories. For a complete list of the advisories and links to them, see Cisco Advance Notification for Publication of October 7, 2026, Security Advisories.

In addition, for further documentation of improvements and fixes in Cisco NX-OS Software, see Cisco NX-OS Software Security Hardening Release: October 2026.

Affected products named by the advisory: NX-OS System Software in ACI Mode; Nexus 9000 Series Switches.

Affected versions

Scope: At the time of publication, this vulnerability affected Cisco Nexus 9000 Series Fabric Switches in ACI Mode, regardless of device configuration.

Official advisory · high-confidence parse· fetched 10 hours ago·verify at source

Fixed versions

No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.

Official advisory · high-confidence parse· fetched 10 hours ago·verify at source

Mitigation checklist

Workaround status

There are no workarounds that address this vulnerability.

Official advisory · high-confidence parse· fetched 10 hours ago·verify at source

Sources

Official and corroborating records used to build this advisory.

Cisco Security Advisoriesofficial
Official vendor source used to discover this advisory; it remains the authority for affected products and remediation. Discovered from the machine-readable feed https://sec.cloudapps.cisco.com/security/center/psirtrss20/CiscoSecurityAdvisory.xml; this link opens the Cisco advisory index instead of the raw feed document.
Cisco
Official vendor advisoryofficial
Official advisory page fetched and parsed; accepted detail fields are attributed to this page.
Cisco

Cross-references

Validate CVE metadata against the authoritative registries.

CVE-2026-20038NVD CVE.org MITRE

Official resources

Cisco Nexus (NX-OS) upgrade guide
Official documentation
Official upgrade documentation for Cisco Nexus switches running NX-OS.
Cisco Software Checker
Official documentation
Official tool to confirm whether your exact IOS / IOS XE / NX-OS / ASA / FTD / SD-WAN release is affected and to find the first fixed release.

Discussion(0)

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