CVE-2021-1377: Cisco IOS and IOS XE Software ARP Resource Management Exhaustion Denial of Service Vulnerability

Severity: medium (CVSS 5.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-03-24 · updated 2026-06-17
Weakness: CWE-399

Description

A vulnerability in Address Resolution Protocol (ARP) management of Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated, remote attacker to prevent an affected device from resolving ARP entries for legitimate hosts on the connected subnets. This vulnerability exists because ARP entries are mismanaged. An attacker could exploit this vulnerability by continuously sending traffic that results in incomplete ARP entries. A successful exploit could allow the attacker to cause ARP requests on the device to be unsuccessful for legitimate hosts, resulting in a denial of service (DoS) condition.

Affected products

Cisco IOS: 12.2(6)i1, 15.1(3)svr1, 15.1(3)svr2, 15.1(3)svr3, 15.1(3)svs, 15.1(3)svs1 (+128)
Cisco IOS XE: 3.6.6e, 3.6.7ae, 3.6.7be, 3.6.7e, 3.6.8e, 3.6.9ae (+162)

References

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