cisco-sa-bootp-WuBhNBxAHighCVSS 8.6

Cisco IOS XE Software for Catalyst 9000 Series Switches DHCP Snooping Denial of Service Vulnerability

Published
March 25, 2026
Last Modified
March 25, 2026

🔗 CVE IDs covered (1)

CVE-2026-20084 →

📋 Description

A vulnerability in the DHCP snooping feature of Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause BOOTP packets to be forwarded between VLANs, resulting in a denial of service (DoS) condition.

This vulnerability is due to improper handling of BOOTP packets on Cisco Catalyst 9000 Series Switches. An attacker could exploit this vulnerability by sending BOOTP request packets to an affected device. A successful exploit could allow an attacker to forward BOOTP packets from one VLAN to another, resulting in BOOTP VLAN leakage and potentially leading to high CPU utilization. This makes the device unreachable (either through console or remote management) and unable to forward traffic, resulting in a DoS condition.

Note: This vulnerability can be exploited with either unicast or broadcast BOOTP packets.

Cisco has released software updates that address this vulnerability. There are workarounds that address this vulnerability.

This advisory is part of the March 2026 release of the Cisco IOS and IOS XE Software Security Advisory Bundled Publication. For a complete list of the advisories and links to them, see Cisco Event Response: March 2026 Semiannual Cisco IOS and IOS XE Software Security Advisory Bundled Publication ["https://sec.cloudapps.cisco.com/security/center/viewErp.x?alertId=ERP-75297"].

CVE-2026-20084 — Cisco IOS XE Software DHCP Snooping Denial of Service Vulnerability (CVSS 3.1 8.6, CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H)

🎯 Affected products115

  • Cisco IOS XE Software
  • Cisco IOS XE Software 16.10.1
  • Cisco IOS XE Software 16.10.1e
  • Cisco IOS XE Software 16.10.1s
  • Cisco IOS XE Software 16.11.1
  • Cisco IOS XE Software 16.11.1b
  • Cisco IOS XE Software 16.11.1c
  • Cisco IOS XE Software 16.11.1s
  • Cisco IOS XE Software 16.12.1
  • Cisco IOS XE Software 16.12.1c
  • Cisco IOS XE Software 16.12.1s
  • Cisco IOS XE Software 16.12.2
  • Cisco IOS XE Software 16.12.2s
  • Cisco IOS XE Software 16.12.2t
  • Cisco IOS XE Software 16.12.3
  • Cisco IOS XE Software 16.12.3a
  • Cisco IOS XE Software 16.12.3s
  • Cisco IOS XE Software 16.12.4
  • Cisco IOS XE Software 16.12.4a
  • Cisco IOS XE Software 16.12.5
  • Cisco IOS XE Software 16.12.5b
  • Cisco IOS XE Software 16.12.6
  • Cisco IOS XE Software 16.12.6a
  • Cisco IOS XE Software 16.12.7
  • Cisco IOS XE Software 16.12.8
  • Cisco IOS XE Software 16.6.1
  • Cisco IOS XE Software 16.6.10
  • Cisco IOS XE Software 16.6.2
  • Cisco IOS XE Software 16.6.3
  • Cisco IOS XE Software 16.6.4
  • +85 more not shown

✅ Remediation

Cisco has released software updates that address this vulnerability. https://software.cisco.com Workarounds: There is a workaround that addresses this vulnerability. For environments that do not need to handle BOOTP traffic, configure ip dhcp relay bootp ignore on the affected device. While this workaround has been deployed and was proven successful in a test environment, customers should determine the applicability and effectiveness in their own environment and under their own use conditions. Customers should be aware that any workaround or mitigation that is implemented may negatively impact the functionality or performance of their network based on intrinsic customer deployment scenarios and limitations. Customers should not deploy any workarounds or mitigations before first evaluating the applicability to their own environment and any impact to such environment.

🔗 References (4)