IS-IS Protocol Vulnerability in Arista EOS Devices
CVE-2026-73446

7HIGH

Key Information:

Vendor

Arista Networks

Status
Eos
Vendor
CVE Published:
15 September 2026

What is CVE-2026-73446?

On platforms utilizing Arista EOS with IS-IS configured over a broadcast interface, an unauthenticated user can craft a malicious IS-IS Hello Protocol Data Unit (PDU) that disrupts the established IS-IS adjacency. This vulnerability can lead to significant traffic disruptions, resulting in the loss of IP reachability for advertised prefixes. This highlights a critical issue in network stability, making it imperative for users to apply the necessary updates and mitigations.

Affected Version(s)

EOS 4.36.0 <= 4.36.1F

EOS 4.35.0 <= 4.35.5M

EOS 4.34.0 <= 4.34.7.1M

References

https://www.arista.com/en/support/advisories-notices/secu...
vendor-advisory

CVSS V4

Score:
7
Severity:
HIGH
Confidentiality:
None
Integrity:
None
Availability:
High
Attack Vector:
Adjacent Network
Attack Complexity:
Low
Attack Required:
Physical
Privileges Required:
Undefined
User Interaction:
None

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

This issue was discovered internally by Arista and the company is not aware of any malicious uses of these issues in customer networks.
.