A vulnerability in the endpoint group (EPG) contract functionality of Cisco Nexus 9000 Series Fabric Switches in ACI Mode could allow an… (CVE-2026-20038)

CVE-2026-20038 describes a vulnerability in the EPG contract functionality of Cisco Nexus 9000 Series Fabric Switches operating in ACI Mode. The flaw arises from improper control enforcement on EPG contracts, which can be bypassed when an attacker sends IPv4 or IPv6 UDP packets with source and destination ports assigned to DHCP traffic. This bypass allows the attacker to circumvent the intended network segmentation enforced by EPG contracts.

The vulnerability allows an unauthenticated remote attacker to bypass EPG contracts, potentially enabling unauthorized communication between endpoint groups. The CVSS score of 5.8 (medium severity) reflects limited impact on confidentiality but a low impact on integrity and no impact on availability. There are no known exploits in the wild at this time.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. No official fix or patch information is provided in the available data. Until a patch is available, network administrators should monitor for unusual DHCP traffic patterns and consider applying any recommended vendor mitigations once published.