CVE-2021-1377

CVE-2021-1377 is a medium-severity vulnerability in Cisco Ios with a CVSS 3.x base score of 5.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-399.

Key facts

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.

Frequently asked questions

What is CVE-2021-1377?
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.
How severe is CVE-2021-1377?
CVE-2021-1377 has a CVSS 3.x base score of 5.8, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability low.
Is CVE-2021-1377 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (70th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-1377?
CVE-2021-1377 primarily affects Cisco Ios. In total, 302 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-1377?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-1377 published?
CVE-2021-1377 was published on 2021-03-24 and last updated on 2026-06-17.

References

Affected products (302)

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