CVE-2026-77190

Adjacent routing-service interruption via malformed PIM messages

Published Sep 16, 2026 · Updated Sep 16, 2026

Improper input validation in Arista EOS allows network-adjacent attackers to crash the Pimsm agent with malformed PIM messages. The Pimsm agent fails to reject malformed PIM Sparse Mode messages and terminates while processing them. Exposure requires PIM Sparse Mode and active MLAG on an affected platform; repeated messages force continuous restarts and sustain a routing-service interruption.

CVSS severity6.5
Medium
EPSS probabilityUnavailable
No score available in this record
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

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Summary

What happened

Improper input validation in Arista EOS allows network-adjacent attackers to crash the Pimsm agent with malformed PIM messages. The Pimsm agent fails to reject malformed PIM Sparse Mode messages and terminates while processing them. Exposure requires PIM Sparse Mode and active MLAG on an affected platform; repeated messages force continuous restarts and sustain a routing-service interruption.

The record

CVE
CVE-2026-77190
Published
Sep 16, 2026
Updated
Sep 16, 2026
Vendor
Arista Networks
Product
Arista EOS
Classifications
CWE-20, T1499.004
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 16, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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

  1. Affected versionversion=4.34.2F <=4.34.7M
  2. Affected versionversion=4.35.0F <=4.35.5M
  3. Affected versionversion=4.36.0F <=4.36.1F

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

Arista Networks · Arista EOSversion=4.34.2F <=4.34.7M; version=4.35.0F <=4.35.5M; version=4.36.0F <=4.36.1F

Published CVSS scores

6.0Arista NetworksCVSS:4.0/AV:A/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L
6.5Arista NetworksCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/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 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-20Improper Input Validation
T1499.004Application or System Exploitation

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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