CVE-2026-73458Network attack vector

Routing disruption via authenticated BFD session teardown

Published Sep 15, 2026 · Updated Sep 15, 2026

Denial of service in authenticated BFD sessions in Arista EOS 4.36.1F and earlier allows remote attackers to disrupt routing. Arista has not disclosed which BFD authentication check mishandles the crafted packet; the observable result is teardown of authenticated sessions. Exposure requires an operational BFD session using Password, Keyed MD5, Meticulous MD5, Keyed SHA1, or Meticulous SHA1 authentication.

CVSS severity8.2
High
EPSS probability0.38%
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 authenticated BFD sessions in Arista EOS 4.36.1F and earlier allows remote attackers to disrupt routing. Arista has not disclosed which BFD authentication check mishandles the crafted packet; the observable result is teardown of authenticated sessions. Exposure requires an operational BFD session using Password, Keyed MD5, Meticulous MD5, Keyed SHA1, or Meticulous SHA1 authentication.

The record

CVE
CVE-2026-73458
Published
Sep 15, 2026
Updated
Sep 15, 2026
Vendor
Arista Networks
Product
Arista EOS
Classifications
CWE-303, T1498
Attack vector
network
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=4.33.0 <=4.33.8M changes=[{"at":"4.33.9M","status":"unaffected"}]
  2. Affected versionversion=4.34.0 <=4.34.7M changes=[{"at":"4.34.8M","status":"unaffected"}]
  3. Affected versionversion=4.35.0 <=4.35.5M changes=[{"at":"4.35.6M","status":"unaffected"}]
  4. Affected versionversion=4.36.0 <=4.36.1F changes=[{"at":"4.36.2F","status":"unaffected"}]

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Arista Networks · Arista EOSversion=4.33.0 <=4.33.8M changes=[{"at":"4.33.9M","status":"unaffected"}]; version=4.34.0 <=4.34.7M changes=[{"at":"4.34.8M","status":"unaffected"}]; version=4.35.0 <=4.35.5M changes=[{"at":"4.35.6M","status":"unaffected"}]; version=4.36.0 <=4.36.1F changes=[{"at":"4.36.2F","status":"unaffected"}]

Published CVSS scores

9.2Arista NetworksCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:H
8.2Arista NetworksCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A: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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-303Incorrect Implementation of Authentication Algorithm
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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