October 3, 2023

Cisco has patched a high-severity DoS vulnerability, tracked as CVE-2023-20049 with a CVSS score of 8.6, in IOS XR software installed in routers.

The vulnerability resides in the bidirectional forwarding detection hardware offload feature of Cisco IOS XR Software for Cisco ASR 9000 Series Aggregation Services Routers, ASR 9902 and ASR 9903 Compact High-Performance Routers.

An unauthenticated remote attacker can trigger the flaw to cause a line card to reset, resulting in a denial of service condition.


An attacker can trigger the CVE-2023-20049 vulnerability by sending a crafted IPv4 BFD packet to a vulnerable device.A successful exploit could allow the attacker to cause line card exceptions or a hard reset, resulting in loss of traffic over that line card while the line card reloads.

This vulnerability does not affect the following Cisco products:

  • IOS Software
  • IOS XE Software
  • IOS XR Platforms

Cisco recommends disabling the BFD hardware offload and creating infrastructure access. Control lists as a workaround Cisco addressed the issue with the release of IOS XR versions 7.5.3, 7.6.2, and 7.7.1

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