CVE-2026-73435 PUBLISHED

Security Advisory 0171

Assigner: Arista
Reserved: 12.08.2026 Published: 16.09.2026 Updated: 16.09.2026

On affected platforms running Arista EOS with Open Shortest Path First version 2 (OSPFv2) configured, a specially crafted OSPFv2 packet from an unauthenticated attacker on the same broadcast segment, with OSPFv2 authentication configured can cause adjacency flapping and packet loss. The disruption can affect routing across the broader OSPF domain.

CVSS Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:H
CVSS Score: 8.2

Attack Vector	Adjacent Network	Scope	Changed
Attack Complexity	Low	Confidentiality Impact	None
Privileges Required	None	Integrity Impact	Low
User Interaction	None	Availability Impact	High

CVSS 3.1

CVSS Vector: CVSS:4.0/AV:A/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H
CVSS Score: 7

Exploitability Metrics		Vulnerable System Impact Metrics		Subsequent System Impact Metrics
Attack Vector	Adjacent	Confidentiality	None	Confidentiality	None
Attack Complexity	Low	Integrity	None	Integrity	None
Attack Requirements	Present	Availability	High	Availability	High
Privileges Required	None
User Interaction	None

CVSS 4.0

Product Status

Vendor	Arista Networks
Product	EOS
Versions	Default: unaffected affected from 4.36.0F to 4.36.1F (incl.) affected from 4.35.0F to 4.35.5M (incl.) affected from 4.34.0F to 4.34.7M (incl.) affected from 4.33.0F to 4.33.9M (incl.) affected from 1.0.0 to 4.33.0F (excl.)

Affected Configurations

In order to be vulnerable to CVE-2026-73435, all of the following conditions must be met:

The vulnerable OSPFv2 instance must have at least two neighbors on the same interface.
The interface is a broadcast interface.
OSPFv2 cryptographic authentication is configured.

Workarounds

No mitigation is available for CVE-2026-73435.

Solutions

The recommended resolution is to upgrade to a remediated software version at your earliest convenience. Arista recommends customers move to the latest version of each release that contains all the fixes listed below.

CVE-2026-73435 has been fixed in the following releases: - 4.36.2F and later releases in the 4.36.x train - 4.35.6M and later releases in the 4.35.x train - 4.34.7.1M and later releases in the 4.34.x train - 4.33.10M and later releases in the 4.33.x train

A hotfix is available for the following releases: 4.36.1F, 4.35.5M, 4.34.7M, 4.33.9M. URL: https://www.arista.com/support/advisories-notices/sa-download/?sa171-SecurityAdvisory171_CVE-2026-73435.swix SWIX hash (SHA512): 4c4ff053d8165f347b45dfcafc2d20396e3eb00869b0088f3128be7f53b2a028b479fa8279849c800b5916ab9aaf8077718a68e3bf4277d55b44076650de0aa7 Note: Installing/uninstalling the SWIX will cause the Ospf process to restart.

References

Security Advisory 0171

Problem Types

CWE-345 Insufficient Verification of Data Authenticity CWE