CVE-2026-73446

Routing disruption via crafted IS-IS Hello PDU

Published Sep 15, 2026 · Updated Sep 15, 2026

Denial of service in affected Arista EOS releases allows remote attackers to disrupt routing with a crafted IS-IS Hello PDU. EOS incorrectly processes the crafted Hello on a broadcast interface by tearing down an established IS-IS adjacency rather than preserving protocol state. Exploitation requires Layer 2 access, IS-IS on a broadcast interface, and an active adjacency; lost routes can interrupt IP reachability.

CVSS severity7.0
High
EPSS probability0.25%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in affected Arista EOS releases allows remote attackers to disrupt routing with a crafted IS-IS Hello PDU. EOS incorrectly processes the crafted Hello on a broadcast interface by tearing down an established IS-IS adjacency rather than preserving protocol state. Exploitation requires Layer 2 access, IS-IS on a broadcast interface, and an active adjacency; lost routes can interrupt IP reachability.

The record

CVE
CVE-2026-73446
Published
Sep 15, 2026
Updated
Sep 15, 2026
Vendor
Arista Networks
Product
Arista EOS
Classifications
CWE-696, T1498
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 15, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 15, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=4.31.0 <4.32.0F
  2. Affected versionversion=4.32.0 <4.33.0F
  3. Affected versionversion=4.33.0 <=4.33.9M
  4. Affected versionversion=4.34.0 <=4.34.7.1M
  5. Affected versionversion=4.35.0 <=4.35.5M
  6. Affected versionversion=4.36.0 <=4.36.1F

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

Arista Networks · Arista EOSversion=4.31.0 <4.32.0F; version=4.32.0 <4.33.0F; version=4.33.0 <=4.33.9M; version=4.34.0 <=4.34.7.1M; version=4.35.0 <=4.35.5M; version=4.36.0 <=4.36.1F

Published CVSS scores

7.4Arista NetworksCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
7.0Arista NetworksCVSS: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 describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-696Incorrect Behavior Order
T1498Network Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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