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Vulnerabilities

Vulnerability · CVE-2025-20340

A vulnerability in the Address Resolution Protocol (ARP) implementation of Cisco IOS XR Software could allow an unauthenticated, adjacent attacker to trigger a broadcast storm, lea

Published Sep 10, 2025 · catalog updated Sep 10, 2025 · Cisco Cisco IOS XR Software

Last checked Oct 23, 2026. A connected source was read within the last 7 days.

Check if you run it

No confirmed exploitation is on record for CVE-2025-20340. EPSS is 0.64%. Act only if a listed version of Cisco Cisco IOS XR Software is installed.

Gaps on this record

  • No vendor fix or required action is stored. Compare the linked advisory before you change production.

Same product and reporting

Severity
High7.4
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.64%
Remediation
Advisory link
Affected products
vendor Cisco Cisco IOS XR Software 7.7.21

A vulnerability in the Address Resolution Protocol (ARP) implementation of Cisco IOS XR Software could allow an unauthenticated, adjacent attacker to trigger a broadcast storm, leading to a denial of service (DoS) condition on an affected device. This vulnerability is due to how Cisco IOS XR Software processes a high, sustained rate of ARP traffic hitting the management interface. Under certain conditions, an attacker could exploit this vulnerability by sending an excessive amount of traffic to the management interface of an affected device, overwhelming its ARP processing capabilities. A succ

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • vendor Cisco Cisco IOS XR Software 7.7.217.7.21

How to fix CVE-2025-20340

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2025-20340. EPSS is 0.64%. Act only if a listed version of Cisco Cisco IOS XR Software is installed.

Which versions are affected?

Compare what you have installed with Cisco Cisco IOS XR Software 7.7.21 7.7.21. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

No weakness class is stored. EPSS 0.64%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Technology hubs

Cisco security

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Sep 10, 2025 · EUVD

    Detected

    A vulnerability in the Address Resolution Protocol (ARP) implementation of Cisco IOS XR Software could allow an unauthenticated, adjacent attacker to trigger a broadcast storm, leading to a denial of service (DoS) condition on an affected device. This vulnerability is due to how Cisco IOS XR Software processes a high, sustained rate of ARP traffic hitting the management interface. Under certain co

  2. Sep 10, 2025 · EUVD

    Updated

    A vulnerability in the Address Resolution Protocol (ARP) implementation of Cisco IOS XR Software could allow an unauthenticated, adjacent attacker to trigger a broadcast storm, leading to a denial of service (DoS) condition on an affected device. This vulnerability is due to how Cisco IOS XR Software processes a high, sustained rate of ARP traffic hitting the management interface. Under certain co

Sources

  • CVE.orgVulnerability recordCVE-2025-20340

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2025-20340

    30-day exploitation probability 0.64%

    first.org
  • EUVDVulnerability recordEUVD-2025-27573

    A vulnerability in the Address Resolution Protocol (ARP) implementation of Cisco IOS XR Software could allow an unauthenticated, adjacent attacker to trigger a broadcast storm, leading to a denial of service (DoS) condition on an affected device. This vulnerability is due to how

    euvd.enisa.europa.eu

References

Freshness

Last verified in this catalog Oct 23, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • FIRST EPSSOct 23, 2026
  • CVE.orgOct 22, 2026
  • EUVDOct 22, 2026