CVE-2023-20027: Cisco IOS XE Software Virtual Fragmentation Reassembly Denial of Service Vulnerability

Severity: high (CVSS 8.6 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.0% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2023-03-23 · updated 2026-06-17
Weakness: CWE-416

Description

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: 3.9.0as, 3.9.1s, 3.9.2s, 3.10.0s, 3.10.1s, 3.10.2as (+184)

References

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