CVE-2025-20311 Denial of service in Cisco IOS XE Software

High 7.4 Published 24 Sep 2025 Updated 30 Sep 2025

An unauthenticated adjacent attacker can cause a denial of service by sending crafted Ethernet frames to block egress ports on Cisco Catalyst switches.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Local or same network only
Victim action needed: Not needed
Fix: None listed

What is CVE-2025-20311?

CVE-2025-20311 is a high-severity denial of service vulnerability in Cisco Ios Xe, published on 24 Sep 2025. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

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.

Weakness: CWE-19

Which versions are affected by CVE-2025-20311?

It affects 1 product.

Products include Cisco Ios Xe.

How do I fix CVE-2025-20311?

No fix has been published for CVE-2025-20311 yet. Limit exposure of the affected software until one is available.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2025-20311 being exploited?

There is no known exploitation of CVE-2025-20311 in the wild and no public exploit code.

All Cisco Ios Xe vulnerabilities

Sources

Also known as GHSA-pr4q-4px5-72j6.