Description
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.
Published: 2026-09-16
Score: 7 High
EPSS: < 1% Very Low
KEV: No
Impact: Denial of Service to routing infrastructure
Action: Immediate Patch
AI Analysis

Impact

A crafted OSPFv2 packet from an unauthenticated host on the same broadcast segment, when OSPFv2 authentication is enabled, triggers adjacency flapping and packet loss, potentially disrupting routing across the OSP compromise network availability by causing routing instability.

Affected Systems

Arista Networks EOS firmware in the 4.36.x, 4.35.x, 4.34.x, and 4.33.x release trains is affected. Fixed releases begin with 4.36.2F 4.34.7.1M, and 4.33.10M respectively, and hotfixes are available for 4.36.1F, 4.35.5M, 4.34.7M, and 4.33.9M.

Risk and Exploitability

The CVSS score of 7 indicates moderate severity, and the vulnerability is not listed in the CISA KEV catalog. With no EPSS data, the exact exploitation probability is unknown, but the vulnerability is locally exploitable by an attacker on the same broadcast segment. Because it causes OSPF adjacency flapping and can lead to packet loss, it constitutes a serious denial‑of‑service risk for any network relying on OSPF for routing.

Generated by OpenCVE AI on September 16, 2026 at 13:52 UTC.

Remediation

Vendor Solution

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.

Vendor Workaround

No mitigation is available for CVE-2026-73435.

OpenCVE Recommended Actions

  • Upgrade to a firmware version that contains the remediation, such as 4.36.2F or later releases in each train, or apply the appropriate SWIX hotfix for the current version. The SWIX installation will restart the OSPF process, so schedule the operation during a maintenance window.
  • After applying the fix, verify for flapping events to confirm that the issue is resolved.
  • If an immediate upgrade is not possible, isolate the affected OSPF interfaces to a separate broadcast domain or block OSPFv2 packets from untrusted hosts until the patch can be deployed.

Generated by OpenCVE AI on September 16, 2026 at 13:52 UTC.

Tracking

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Advisories

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History

Wed, 16 Sep 2026 16:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Wed, 16 Sep 2026 09:30:00 +0000

Type Values Removed Values Added
Description 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.
Title Security Advisory 0171
Weaknesses CWE-345
References
Metrics cvssV3_1

{'score': 8.2, 'vector': 'CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:H'}

cvssV4_0

{'score': 7, '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'}

Subscriptions

No data.

cve-icon MITRE

Status: PUBLISHED

Assigner: Arista

Published:

Updated: 2026-09-16T15:29:43.316Z

Reserved: 2026-08-12T16:39:35.976Z

Link: CVE-2026-73435

cve-icon Vulnrichment

Updated: 2026-09-16T15:29:35.559Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-09-16T10:16:51.363

Modified: 2026-09-16T19:09:28.447

Link: CVE-2026-73435

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-09-16T14:00:11Z

Weaknesses
  • CWE-345

    Insufficient Verification of Data Authenticity