---
id: CVE-2025-20311
title: >-
  A vulnerability in the handling of certain Ethernet frames in Cisco IOS XE
  Software for Catalyst 9000 Series Switches could allow an unauthenticated,
  adjacent attacker to cause an egress port to become blocked and drop all
  outbound traff…
summary: >-
  A vulnerability in the handling of certain Ethernet frames in Cisco IOS XE
  Software for Catalyst 9000 Series Switches could allow an unauthenticated,
  adjacent attacker to cause an egress port to become blocked and drop all
  outbound traff…
severity: high
cvss: 7.4
cvssVector: 'CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H'
cwe:
  - CWE-19
vendor: cisco
product: ios_xe
affected:
  - ios_xe = 16.6.1
  - ios_xe = 16.6.2
  - ios_xe = 16.6.3
  - ios_xe = 16.6.4
  - ios_xe = 16.6.4a
  - ios_xe = 16.6.5
  - ios_xe = 16.6.6
  - ios_xe = 16.6.7
  - ios_xe = 16.6.8
  - ios_xe = 16.6.9
  - ios_xe = 16.6.10
  - ios_xe = 16.7.1
  - ios_xe = 16.8.1
  - ios_xe = 16.8.1a
  - ios_xe = 16.8.1s
  - ios_xe = 16.9.1
  - ios_xe = 16.9.1s
  - ios_xe = 16.9.2
  - ios_xe = 16.9.3
  - ios_xe = 16.9.4
  - ios_xe = 16.9.5
  - ios_xe = 16.9.6
  - ios_xe = 16.9.7
  - ios_xe = 16.9.8
  - ios_xe = 16.10.1
  - ios_xe = 16.10.1e
  - ios_xe = 16.10.1s
  - ios_xe = 16.11.1
  - ios_xe = 16.11.1b
  - ios_xe = 16.11.1s
  - ios_xe = 16.12.1
  - ios_xe = 16.12.1c
  - ios_xe = 16.12.1s
  - ios_xe = 16.12.2
  - ios_xe = 16.12.2s
  - ios_xe = 16.12.3
  - ios_xe = 16.12.3a
  - ios_xe = 16.12.3s
  - ios_xe = 16.12.4
  - ios_xe = 16.12.4a
  - ios_xe = 16.12.5
  - ios_xe = 16.12.5b
  - ios_xe = 16.12.6
  - ios_xe = 16.12.6a
  - ios_xe = 16.12.7
  - ios_xe = 16.12.8
  - ios_xe = 16.12.14
  - ios_xe = 17.1.1
  - ios_xe = 17.1.1s
  - ios_xe = 17.1.1t
  - ios_xe = 17.1.3
  - ios_xe = 17.2.1
  - ios_xe = 17.2.1a
  - ios_xe = 17.3.1
  - ios_xe = 17.3.2
  - ios_xe = 17.3.2a
  - ios_xe = 17.3.3
  - ios_xe = 17.3.4
  - ios_xe = 17.3.4b
  - ios_xe = 17.3.5
  - ios_xe = 17.3.6
  - ios_xe = 17.3.7
  - ios_xe = 17.3.8
  - ios_xe = 17.3.8a
  - ios_xe = 17.4.1
  - ios_xe = 17.5.1
  - ios_xe = 17.6.1
  - ios_xe = 17.6.1y
  - ios_xe = 17.6.2
  - ios_xe = 17.6.3
  - ios_xe = 17.6.4
  - ios_xe = 17.6.5
  - ios_xe = 17.6.5a
  - ios_xe = 17.6.6
  - ios_xe = 17.6.6a
  - ios_xe = 17.6.7
  - ios_xe = 17.6.8
  - ios_xe = 17.7.1
  - ios_xe = 17.8.1
  - ios_xe = 17.9.1
  - ios_xe = 17.9.2
  - ios_xe = 17.9.3
  - ios_xe = 17.9.4
  - ios_xe = 17.9.4a
  - ios_xe = 17.9.5
  - ios_xe = 17.9.6
  - ios_xe = 17.9.6a
  - ios_xe = 17.10.1
  - ios_xe = 17.10.1b
  - ios_xe = 17.11.1
  - ios_xe = 17.11.99sw
  - ios_xe = 17.12.1
  - ios_xe = 17.12.1z3
  - ios_xe = 17.12.2
  - ios_xe = 17.12.3
  - ios_xe = 17.12.4
  - ios_xe = 17.13.1
  - ios_xe = 17.14.1
  - ios_xe = 17.15.1
  - ios_xe = 17.15.2
published: '2025-09-24'
updated: '2026-09-18'
sourceUpdated: '2026-09-18T10:39:07.903'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2025-20311'
references:
  - url: >-
      https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-cat9k-PtmD7bgy
    label: psirt@cisco.com
tags:
  - nvd
epss: 0.00202
epssPercentile: 0.10375
ingestedAt: '2026-09-17T20:28:02.737Z'
---

## Overview

A vulnerability in the handling of certain Ethernet frames in Cisco IOS XE Software for Catalyst 9000 Series Switches could allow an unauthenticated, adjacent attacker to cause an egress port to become blocked and drop all outbound traffic.

 This vulnerability is due to improper handling of crafted Ethernet frames. An attacker could exploit this vulnerability by sending crafted Ethernet frames through an affected switch. A successful exploit could allow the attacker to cause the egress port to which the crafted frame is forwarded to start dropping all frames, resulting in a denial of service (DoS) condition.

## Affected

- `ios_xe = 16.6.1`
- `ios_xe = 16.6.2`
- `ios_xe = 16.6.3`
- `ios_xe = 16.6.4`
- `ios_xe = 16.6.4a`
- `ios_xe = 16.6.5`
- `ios_xe = 16.6.6`
- `ios_xe = 16.6.7`
- `ios_xe = 16.6.8`
- `ios_xe = 16.6.9`
- `ios_xe = 16.6.10`
- `ios_xe = 16.7.1`
- `ios_xe = 16.8.1`
- `ios_xe = 16.8.1a`
- `ios_xe = 16.8.1s`
- `ios_xe = 16.9.1`
- `ios_xe = 16.9.1s`
- `ios_xe = 16.9.2`
- `ios_xe = 16.9.3`
- `ios_xe = 16.9.4`
- `ios_xe = 16.9.5`
- `ios_xe = 16.9.6`
- `ios_xe = 16.9.7`
- `ios_xe = 16.9.8`
- `ios_xe = 16.10.1`
- `ios_xe = 16.10.1e`
- `ios_xe = 16.10.1s`
- `ios_xe = 16.11.1`
- `ios_xe = 16.11.1b`
- `ios_xe = 16.11.1s`
- `ios_xe = 16.12.1`
- `ios_xe = 16.12.1c`
- `ios_xe = 16.12.1s`
- `ios_xe = 16.12.2`
- `ios_xe = 16.12.2s`
- `ios_xe = 16.12.3`
- `ios_xe = 16.12.3a`
- `ios_xe = 16.12.3s`
- `ios_xe = 16.12.4`
- `ios_xe = 16.12.4a`
- `ios_xe = 16.12.5`
- `ios_xe = 16.12.5b`
- `ios_xe = 16.12.6`
- `ios_xe = 16.12.6a`
- `ios_xe = 16.12.7`
- `ios_xe = 16.12.8`
- `ios_xe = 16.12.14`
- `ios_xe = 17.1.1`
- `ios_xe = 17.1.1s`
- `ios_xe = 17.1.1t`
- `ios_xe = 17.1.3`
- `ios_xe = 17.2.1`
- `ios_xe = 17.2.1a`
- `ios_xe = 17.3.1`
- `ios_xe = 17.3.2`
- `ios_xe = 17.3.2a`
- `ios_xe = 17.3.3`
- `ios_xe = 17.3.4`
- `ios_xe = 17.3.4b`
- `ios_xe = 17.3.5`
- `ios_xe = 17.3.6`
- `ios_xe = 17.3.7`
- `ios_xe = 17.3.8`
- `ios_xe = 17.3.8a`
- `ios_xe = 17.4.1`
- `ios_xe = 17.5.1`
- `ios_xe = 17.6.1`
- `ios_xe = 17.6.1y`
- `ios_xe = 17.6.2`
- `ios_xe = 17.6.3`
- `ios_xe = 17.6.4`
- `ios_xe = 17.6.5`
- `ios_xe = 17.6.5a`
- `ios_xe = 17.6.6`
- `ios_xe = 17.6.6a`
- `ios_xe = 17.6.7`
- `ios_xe = 17.6.8`
- `ios_xe = 17.7.1`
- `ios_xe = 17.8.1`
- `ios_xe = 17.9.1`
- `ios_xe = 17.9.2`
- `ios_xe = 17.9.3`
- `ios_xe = 17.9.4`
- `ios_xe = 17.9.4a`
- `ios_xe = 17.9.5`
- `ios_xe = 17.9.6`
- `ios_xe = 17.9.6a`
- `ios_xe = 17.10.1`
- `ios_xe = 17.10.1b`
- `ios_xe = 17.11.1`
- `ios_xe = 17.11.99sw`
- `ios_xe = 17.12.1`
- `ios_xe = 17.12.1z3`
- `ios_xe = 17.12.2`
- `ios_xe = 17.12.3`
- `ios_xe = 17.12.4`
- `ios_xe = 17.13.1`
- `ios_xe = 17.14.1`
- `ios_xe = 17.15.1`
- `ios_xe = 17.15.2`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.