--- 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: '2026-09-26' sourceUpdated: '2026-09-26T00:10:00.127' 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 - url: 'https://software.cisco.com' tags: - nvd - csaf - vendor-advisory - cisco epss: 0.00202 epssPercentile: 0.0999 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. ## Vendor advisories - **cisco-sa-cat9k-PtmD7bgy** · Cisco · affected: Cisco IOS XE Software (148 versions) · updated 2025-09-30 · [advisory](https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-cat9k-PtmD7bgy)