CVE-2023-20027: Cisco IOS XE

High severity, CVSS 8.6. EPSS: 1% chance of exploitation in the next 30 days.

A vulnerability in the implementation of the IPv4 Virtual Fragmentation Reassembly (VFR) feature of Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to improper reassembly of large packets that occurs when VFR is enabled on either a tunnel interface or on a physical interface that is configured with a maximum transmission unit (MTU) greater than 4,615 bytes. An attacker could exploit this vulnerability by sending fragmented packets through a VFR-enabled interface on an affected device. A successful exploit could allow the attacker to cause the device to reload, resulting in a DoS condition.

Affected products

• Cisco IOS XE: version 3.9.0as only; version 3.9.1s only; version 3.9.2s only; version 3.10.0s only; version 3.10.1s only; version 3.10.2as only; …

Published 2023-03-23. Last modified 2026-06-17.