{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-77191", "assignerOrgId": "c8b34d1a-69ae-45c3-88fe-f3b3d44f39b7", "state": "PUBLISHED", "assignerShortName": "Arista", "dateReserved": "2026-08-20T16:41:22.053Z", "datePublished": "2026-09-14T22:06:28.153Z", "dateUpdated": "2026-09-14T22:06:28.153Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "c8b34d1a-69ae-45c3-88fe-f3b3d44f39b7", "shortName": "Arista", "dateUpdated": "2026-09-14T22:06:28.153Z"}, "title": "All of the CVEs covered in this advisory apply to affected platforms running Arista EOS with 802.1X authentication and authorization enabled and Access Control Lists (ACLs) configured for per-supplicant policy enforcement. An authenticated supplicant on an", "datePublic": "2026-09-09T22:02:00.000Z", "problemTypes": [{"descriptions": [{"lang": "en", "cweId": "CWE-862", "description": "CWE-862 Missing Authorization", "type": "CWE"}]}], "impacts": [{"capecId": "CAPEC-180", "descriptions": [{"lang": "en", "value": "CAPEC-180 Exploiting Incorrectly Configured Access Control Security Levels"}]}], "affected": [{"vendor": "Arista Networks", "product": "EOS", "versions": [{"status": "affected", "version": "4.35.0", "lessThanOrEqual": "4.35.0.3F", "versionType": "custom"}, {"status": "affected", "version": "4.34.0", "lessThanOrEqual": "4.34.5M", "versionType": "custom"}, {"status": "affected", "version": "0.0.0", "lessThanOrEqual": "4.33.7.1M", "versionType": "custom"}], "defaultStatus": "unaffected"}], "descriptions": [{"lang": "en", "value": "An authenticated supplicant on an adjacent network may bypass intended network authorization policy and send unrestricted traffic during a brief window (milliseconds to seconds) between the completion of the authentication phase and the full enforcement of its assigned ACL.", "supportingMedia": [{"type": "text/html", "base64": false, "value": "<pre>An authenticated supplicant on an adjacent network may bypass intended network authorization policy and send unrestricted traffic during a brief window (milliseconds to seconds) between the completion of the authentication phase and the full enforcement of its assigned ACL.\n</pre>"}]}], "references": [{"url": "https://www.arista.com/en/support/advisories-notices/security-advisory/24706-security-advisory-0150"}], "configurations": [{"lang": "en", "value": "In order to be vulnerable to any of the vulnerabilities, the following condition must be met under interface configuration mode:\n\n * 802.1X (dot1x in the CLI) must be configured with pae authenticator\u00a0\n\n\n * port-control must be set to auto mode\u00a0\n\n\n * A static or dynamic ACL must be configured.\u00a0\n\n\n * The RADIUS Access-Accept or Change-of-Authorization (CoA) assigns an ACL to that supplicant using RADIUS AVP (Attribute-Value pair) Filter-Id or NAS-Filter-Rule\n\u00a0\n\n\n\nBelow is an example of one configuration. Note that \u201cmac based authentication always\u201d is optional The supplicant can authenticate with either EAPOL or MBA.\n\n\n\nswitch(config-if-et1)#show active\n \ninterface Ethernet5\n\u00a0\u00a0\u00a0switchport mode trunk\n\u00a0\u00a0\u00a0spanning-tree portfast edge\n dot1x pae authenticator\n\u00a0\u00a0\u00a0dot1x port-control auto\n \ndot1x system-auth-control\n\n\n\u00a0\n\n\n\nIn this example port control is in \u201cauto\u201d mode, necessary for the condition to occur.\n\n\n\nconfig)#show\u00a0 dot1x\u00a0 interface\u00a0 ethernet 5 details\nDot1X Information for Ethernet5\n--------------------------------------------\nPort control: auto\nForced phone authorization: disabled\nEAPOL: enabled\nHost mode: multi-host\nMAC-based authentication: enabled\nMAC-based authentication host mode: Unconfigured\nMAC-based authentication always: enabled\nQuiet period: 60 seconds\nTX period: 5 seconds\nMaximum reauth requests: 2\nIgnore reauth timeout: No\nAuth failure VLAN: Unconfigured\nUnauthorized access VLAN egress: No\nUnauthorized native VLAN egress: No\nEAPOL authentication failure fallback: Unconfigured\nPort ErrDisabled by CoA: no\n \nDot1X Authenticator Client\n\n\n\u00a0\n\n\n\n\u00a0 Use a preconfigured ACL with which the RADIUS server returns in the Filter-Id AVP\n\n\n\nswitch(config)#ip access-list EMPLOYEE-ACL\nswitch(config-ip-acl-EMPLOYEE-ACL)#10 permit ip 10.0.0.0/8 any\nswitch(config-ip-acl-EMPLOYEE-ACL)#20 deny ip any any\n\n\n\u00a0\n\n\n\nAAA server will return the ACL name through Filter-Id AVP through Access-Accept or CoA messages , in the above sample , Filter-Id AVP with EMPLOYEE-ACL will be received from the server.\n\n\n\nTo verify the configured ACL, execute the following show command to identify the ACL applied to the interface:\n\n\n\nswitch(config)#show ip access-lists interface Ethernet5 summary\u00a0\nIP Access List EMPLOYEE-ACL\n\u00a0\u00a0\u00a010 permit ip 10.0.0.0/8 any\n\u00a0\u00a0\u00a020 deny ip any any\n \n\u00a0\u00a0\u00a0Total rules configured: 2\n\u00a0\u00a0\u00a0Configured on Ingress: Ethernet5\n\u00a0\u00a0\u00a0Active on Ingress: Ethernet5", "supportingMedia": [{"type": "text/html", "base64": false, "value": "<pre><p>In order to be vulnerable to any of the vulnerabilities, the following condition must be met under interface configuration mode:</p><ol><li>802.1X (dot1x in the CLI) must be configured with <b>pae authenticator</b><div>&nbsp;</div></li><li>port-control must be set to auto mode<div>&nbsp;</div></li><li>A static or dynamic ACL must be configured.<div>&nbsp;</div></li><li>The RADIUS Access-Accept or Change-of-Authorization (CoA) assigns an ACL to that supplicant using RADIUS AVP (Attribute-Value pair) Filter-Id or NAS-Filter-Rule</li></ol><div>&nbsp;</div><p>Below is an example of one configuration. Note that \u201cmac based authentication always\u201d is optional The supplicant can authenticate with either EAPOL or MBA.</p><pre>switch(config-if-et1)#show active\n \ninterface Ethernet5\n&nbsp;&nbsp;&nbsp;switchport mode trunk\n&nbsp;&nbsp;&nbsp;spanning-tree portfast edge\n dot1x pae authenticator\n&nbsp;&nbsp;&nbsp;dot1x port-control auto\n \ndot1x system-auth-control\n</pre><div>&nbsp;</div><p>In this example port control is in \u201cauto\u201d mode, necessary for the condition to occur.</p><pre>config)#show&nbsp; dot1x&nbsp; interface&nbsp; ethernet 5 details\nDot1X Information for Ethernet5\n--------------------------------------------\nPort control: auto\nForced phone authorization: disabled\nEAPOL: enabled\nHost mode: multi-host\nMAC-based authentication: enabled\nMAC-based authentication host mode: Unconfigured\nMAC-based authentication always: enabled\nQuiet period: 60 seconds\nTX period: 5 seconds\nMaximum reauth requests: 2\nIgnore reauth timeout: No\nAuth failure VLAN: Unconfigured\nUnauthorized access VLAN egress: No\nUnauthorized native VLAN egress: No\nEAPOL authentication failure fallback: Unconfigured\nPort ErrDisabled by CoA: no\n \nDot1X Authenticator Client\n</pre><div>&nbsp;</div><p>&nbsp; Use a preconfigured ACL with which the RADIUS server returns in the <b>Filter-Id</b> AVP</p><pre>switch(config)#ip access-list EMPLOYEE-ACL\nswitch(config-ip-acl-EMPLOYEE-ACL)#10 permit ip 10.0.0.0/8 any\nswitch(config-ip-acl-EMPLOYEE-ACL)#20 deny ip any any\n</pre><div>&nbsp;</div><p>AAA server will return the ACL name through <b>Filter-Id</b> AVP through Access-Accept or CoA messages , in the above sample , Filter-Id AVP with EMPLOYEE-ACL will be received from the server.</p><p>To verify the configured ACL, execute the following show command to identify the ACL applied to the interface:</p><pre>switch(config)#show ip access-lists interface Ethernet5 summary&nbsp;\nIP Access List EMPLOYEE-ACL\n&nbsp;&nbsp;&nbsp;10 permit ip 10.0.0.0/8 any\n&nbsp;&nbsp;&nbsp;20 deny ip any any\n \n&nbsp;&nbsp;&nbsp;Total rules configured: 2\n&nbsp;&nbsp;&nbsp;Configured on Ingress: Ethernet5\n&nbsp;&nbsp;&nbsp;Active on Ingress: Ethernet5&nbsp;</pre></pre>"}]}], "workarounds": [{"lang": "en", "value": "There is no workaround available for CVE-2026-77191.", "supportingMedia": [{"type": "text/html", "base64": false, "value": "<pre>\nThere is no workaround available for CVE-2026-77191.\n</pre>"}]}], "solutions": [{"lang": "en", "value": "CVE-2026-77191 has been fixed in the following releases:\n* 4.35.1F and later releases in the 4.35.x train.\n* 4.34.6M and later releases in the 4.34.x train.\n* 4.33.8M and later releases in the 4.33.x train.", "supportingMedia": [{"type": "text/html", "base64": false, "value": "<pre>\nCVE-2026-77191 has been fixed in the following releases:\n* 4.35.1F and later releases in the 4.35.x train.\n* 4.34.6M and later releases in the 4.34.x train.\n* 4.33.8M and later releases in the 4.33.x train.\n</pre>"}]}], "credits": [{"lang": "en", "value": "Those issues were discovered internally by Arista, and the company is not aware of any malicious exploitation of these vulnerabilities in customer networks.", "type": "finder"}], "source": {"advisory": "150", "discovery": "INTERNAL", "defects": ["BUG 1108416"]}, "x_generator": {"engine": "Vulnogram 1.0.5"}, "metrics": [{"format": "CVSS", "scenarios": [{"lang": "en", "value": "GENERAL"}], "cvssV3_1": {"version": "3.1", "attackVector": "ADJACENT_NETWORK", "attackComplexity": "HIGH", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "LOW", "availabilityImpact": "NONE", "baseSeverity": "LOW", "baseScore": 2.6, "vectorString": "CVSS:3.1/AV:A/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N"}}, {"format": "CVSS", "scenarios": [{"lang": "en", "value": "GENERAL"}], "cvssV4_0": {"attackVector": "ADJACENT", "attackComplexity": "LOW", "attackRequirements": "PRESENT", "privilegesRequired": "LOW", "userInteraction": "NONE", "vulnConfidentialityImpact": "NONE", "subConfidentialityImpact": "NONE", "vulnIntegrityImpact": "LOW", "subIntegrityImpact": "NONE", "vulnAvailabilityImpact": "NONE", "subAvailabilityImpact": "NONE", "exploitMaturity": "NOT_DEFINED", "Safety": "NOT_DEFINED", "Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "valueDensity": "NOT_DEFINED", "vulnerabilityResponseEffort": "NOT_DEFINED", "providerUrgency": "NOT_DEFINED", "version": "4.0", "baseSeverity": "LOW", "baseScore": 2.1, "vectorString": "CVSS:4.0/AV:A/AC:L/AT:P/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N"}}]}}}

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{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "product": "EOS", "vendor": "Arista Networks", "versions": [{"lessThanOrEqual": "4.35.0.3F", "status": "affected", "version": "4.35.0", "versionType": "custom"}, {"lessThanOrEqual": "4.34.5M", "status": "affected", "version": "4.34.0", "versionType": "custom"}, {"lessThanOrEqual": "4.33.7.1M", "status": "affected", "version": "0.0.0", "versionType": "custom"}]}], "source": "psirt@arista.com"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "An authenticated supplicant on an adjacent network may bypass intended network authorization policy and send unrestricted traffic during a brief window (milliseconds to seconds) between the completion of the authentication phase and the full enforcement of its assigned ACL."}], "id": "CVE-2026-77191", "lastModified": "2026-09-14T23:18:36.170", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "HIGH", "attackVector": "ADJACENT_NETWORK", "availabilityImpact": "NONE", "baseScore": 2.6, "baseSeverity": "LOW", "confidentialityImpact": "NONE", "integrityImpact": "LOW", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:A/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N", "version": "3.1"}, "exploitabilityScore": 1.2, "impactScore": 1.4, "source": "psirt@arista.com", "type": "Secondary"}], "cvssMetricV40": [{"cvssData": {"Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "Safety": "NOT_DEFINED", "attackComplexity": "LOW", "attackRequirements": "PRESENT", "attackVector": "ADJACENT", "availabilityRequirement": "NOT_DEFINED", "baseScore": 2.1, "baseSeverity": "LOW", "confidentialityRequirement": "NOT_DEFINED", "exploitMaturity": "NOT_DEFINED", "integrityRequirement": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "privilegesRequired": "LOW", "providerUrgency": "NOT_DEFINED", "subAvailabilityImpact": "NONE", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "NONE", "userInteraction": "NONE", "valueDensity": "NOT_DEFINED", "vectorString": "CVSS:4.0/AV:A/AC:L/AT:P/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X", "version": "4.0", "vulnAvailabilityImpact": "NONE", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "LOW", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "source": "psirt@arista.com", "type": "Secondary"}]}, "published": "2026-09-14T23:18:36.170", "references": [{"source": "psirt@arista.com", "url": "https://www.arista.com/en/support/advisories-notices/security-advisory/24706-security-advisory-0150"}], "sourceIdentifier": "psirt@arista.com", "vulnStatus": "Received", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-862"}], "source": "psirt@arista.com", "type": "Secondary"}]}

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