CVE-2026-73443 (GCVE-0-2026-73443)
Vulnerability from cvelistv5 – Published: 2026-09-16 18:47 – Updated: 2026-09-17 18:33
VLAI
EPSS
VEX
Title
On affected platforms running Arista EOS with VRRPv2 IP-AH authentication configured, an unauthenticated attacker within the same layer 2 network segment on which VRRP is running can capture a legitimate authenticated VRRP advertisement and replay it indef
Summary
On affected platforms running Arista EOS with VRRPv2 IP-AH authentication configured, an unauthenticated attacker within the same layer 2 network segment on which VRRP is running can capture a legitimate authenticated VRRP advertisement and replay it indefinitely. Replayed advertisements can be used to advertise stale VRRP state, for example to prevent a backup router from taking over the virtual gateway after the original master has gone down, resulting in a denial of service for hosts using the virtual gateway address.
Severity
4.7 (Medium)
SSVC
Exploitation: none
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-09-17 18:33 UTC
CWE
- CWE-294 - Authentication Bypass by Capture-replay
Assigner
References
1 reference
| URL | Tags |
|---|---|
| https://www.arista.com/en/support/advisories-noti… | vendor-advisory |
Impacted products
1 product
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| Arista Networks | EOS |
Affected:
4.36.0 , ≤ 4.36.1F
(custom)
Affected: 4.35.0 , ≤ 4.35.5M (custom) Affected: 4.34.0 , ≤ 4.34.7M (custom) Affected: 4.33.0 , ≤ 4.33.9M (custom) |
guessed |
Date Public
2026-09-09 18:44
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"value": "\u003cp\u003eOn affected platforms running Arista EOS with VRRPv2 IP-AH authentication configured, an unauthenticated attacker within the same layer 2 network segment on which VRRP is running can capture a legitimate authenticated VRRP advertisement and replay it indefinitely. Replayed advertisements can be used to advertise stale VRRP state, for example to prevent a backup router from taking over the virtual gateway after the original master has gone down, resulting in a denial of service for hosts using the virtual gateway address.\u003c/p\u003e"
}
],
"value": "On affected platforms running Arista EOS with VRRPv2 IP-AH authentication configured, an unauthenticated attacker within the same layer 2 network segment on which VRRP is running can capture a legitimate authenticated VRRP advertisement and replay it indefinitely. Replayed advertisements can be used to advertise stale VRRP state, for example to prevent a backup router from taking over the virtual gateway after the original master has gone down, resulting in a denial of service for hosts using the virtual gateway address."
}
],
"impacts": [
{
"capecId": "CAPEC-60",
"descriptions": [
{
"lang": "en",
"value": "CAPEC-60 Replay Attacks"
}
]
}
],
"metrics": [
{
"cvssV3_1": {
"attackComplexity": "LOW",
"attackVector": "ADJACENT_NETWORK",
"availabilityImpact": "LOW",
"baseScore": 4.7,
"baseSeverity": "MEDIUM",
"confidentialityImpact": "NONE",
"integrityImpact": "NONE",
"privilegesRequired": "NONE",
"scope": "CHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L",
"version": "3.1"
},
"format": "CVSS",
"scenarios": [
{
"lang": "en",
"value": "GENERAL"
}
]
},
{
"cvssV4_0": {
"Automatable": "NOT_DEFINED",
"Recovery": "NOT_DEFINED",
"Safety": "NOT_DEFINED",
"attackComplexity": "LOW",
"attackRequirements": "NONE",
"attackVector": "ADJACENT",
"baseScore": 5.3,
"baseSeverity": "MEDIUM",
"exploitMaturity": "NOT_DEFINED",
"privilegesRequired": "NONE",
"providerUrgency": "NOT_DEFINED",
"subAvailabilityImpact": "NONE",
"subConfidentialityImpact": "NONE",
"subIntegrityImpact": "NONE",
"userInteraction": "NONE",
"valueDensity": "NOT_DEFINED",
"vectorString": "CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N",
"version": "4.0",
"vulnAvailabilityImpact": "LOW",
"vulnConfidentialityImpact": "NONE",
"vulnIntegrityImpact": "NONE",
"vulnerabilityResponseEffort": "NOT_DEFINED"
},
"format": "CVSS",
"scenarios": [
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"value": "GENERAL"
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}
],
"problemTypes": [
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"descriptions": [
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"cweId": "CWE-294",
"description": "CWE-294 Authentication Bypass by Capture-replay",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-09-16T18:47:30.801Z",
"orgId": "c8b34d1a-69ae-45c3-88fe-f3b3d44f39b7",
"shortName": "Arista"
},
"references": [
{
"tags": [
"vendor-advisory"
],
"url": "https://www.arista.com/en/support/advisories-notices/security-advisory/24713-security-advisory-0157"
}
],
"solutions": [
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"lang": "en",
"supportingMedia": [
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"value": "\u003cp\u003eThe recommended resolution is to upgrade to a remediated software version at your earliest convenience.\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eImportant:\u003c/strong\u003e Upgrading alone is not sufficient. The replay protection introduced by the fix is disabled by default and must be explicitly enabled with the following new global configuration command after upgrading to a remediated release:\u003c/p\u003e\u003cpre\u003eswitch(config)#vrrp ipv4 authentication anti-replay\u003c/pre\u003e\u003cp\u003eCVE-2026-73443 has been fixed in the following releases:\u003c/p\u003e\u003cul\u003e\u003cli\u003e4.36.2F and later releases in the 4.36.x train\u003c/li\u003e\u003cli\u003e4.35.6M and later releases in the 4.35.x train\u003c/li\u003e\u003cli\u003e4.34.8M and later releases in the 4.34.x train\u003c/li\u003e\u003cli\u003e4.33.10M and later releases in the 4.33.x train\u003c/li\u003e\u003c/ul\u003e"
}
],
"value": "The recommended resolution is to upgrade to a remediated software version at your earliest convenience.\n\n\n\nImportant: Upgrading alone is not sufficient. The replay protection introduced by the fix is disabled by default and must be explicitly enabled with the following new global configuration command after upgrading to a remediated release:\n\n\n\nswitch(config)#vrrp ipv4 authentication anti-replay\n\n\n\nCVE-2026-73443 has been fixed in the following releases:\n\n * 4.36.2F and later releases in the 4.36.x train\n * 4.35.6M and later releases in the 4.35.x train\n * 4.34.8M and later releases in the 4.34.x train\n * 4.33.10M and later releases in the 4.33.x train"
}
],
"source": {
"advisory": "157",
"defect": [
"1866651"
],
"discovery": "INTERNAL"
},
"title": "On affected platforms running Arista EOS with VRRPv2 IP-AH authentication configured, an unauthenticated attacker within the same layer 2 network segment on which VRRP is running can capture a legitimate authenticated VRRP advertisement and replay it indef",
"workarounds": [
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"value": "\u003cp\u003eExposure is limited to attackers with access to the layer 2 network segment on which VRRP is running. Restricting physical and logical access to VRRP-enabled segments (for example with port security and by not extending VRRP VLANs to untrusted access ports) reduces the attack surface. Additionally, migrating virtual routers from VRRP version 2 with authentication to VRRP version 3 removes the vulnerable code path.\u003c/p\u003e\u003cp\u003eThe below configuration shows how to configure VRRPv3 on VLAN 20:\u003c/p\u003e\u003cpre\u003eswitch(config)# interface vlan 20\nswitch(config-if-vl20)# vrrp 1 ipv4 version 3\u003c/pre\u003e"
}
],
"value": "Exposure is limited to attackers with access to the layer 2 network segment on which VRRP is running. Restricting physical and logical access to VRRP-enabled segments (for example with port security and by not extending VRRP VLANs to untrusted access ports) reduces the attack surface. Additionally, migrating virtual routers from VRRP version 2 with authentication to VRRP version 3 removes the vulnerable code path.\n\n\n\nThe below configuration shows how to configure VRRPv3 on VLAN 20:\n\n\n\nswitch(config)# interface vlan 20\nswitch(config-if-vl20)# vrrp 1 ipv4 version 3"
}
],
"x_generator": {
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"cveMetadata": {
"assignerOrgId": "c8b34d1a-69ae-45c3-88fe-f3b3d44f39b7",
"assignerShortName": "Arista",
"cveId": "CVE-2026-73443",
"datePublished": "2026-09-16T18:47:30.801Z",
"dateReserved": "2026-08-12T16:39:35.977Z",
"dateUpdated": "2026-09-16T18:47:30.801Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.
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