In order to be vulnerable to CVE-2026-73459, the following condition must be met:
IS-IS should be configured.
switch# show isis summary\nIS-IS Instance: 1 VRF: default\n Instance ID: 0\n System ID: 1111.1111.1001, administratively enabled\n Router ID: IPv4: 0.0.0.0\n Multi Topology disabled, not attached\n IPv4 Preference: Level 1: 115, Level 2: 115\n IPv6 Preference: Level 1: 115, Level 2: 115\n IS-Type: Level 1 and 2, Number active interfaces: 1\n Routes both IPv4 and IPv6\n LSP size maximum: Level 1: 1492, Level 2: 1492\n Interval Type Max Wait Initial Wait Hold Interval\n ----------------------- -------- ------------ -------------\n LSP generation interval 5 s 50 ms 50 ms\n SPF interval 30000 ms 300 ms 80 ms\n Current SPF hold interval(ms): Level 1: 80, Level 2: 80\n Last Level 1 SPF run 9 seconds ago\n Last Level 2 SPF run 9 seconds ago\n CSNP generation interval: 10 seconds\n Dynamic Flooding: Disabled\n Authentication mode: Level 1: None, Level 2: None\n Graceful Restart: Disabled, Graceful Restart Helper: Enabled\n Area addresses: 40\n level 1: number DIS interfaces: 0, LSDB size: 1\n Area Leader: None\n Overload Bit is not set. \n level 2: number DIS interfaces: 0, LSDB size: 1\n Area Leader: None\n Overload Bit is not set. \n Redistributed Level 1 routes: 0 limit: Not Configured\n Redistributed Level 2 routes: 0 limit: Not Configured
If IS-IS is not configured, there is no exposure to this issue.
switch#show isis summary\nswitch#"}],"value":"In order to be vulnerable to CVE-2026-73459, the following condition must be met: \n\nIS-IS should be configured.\n\n\n\nswitch# show isis summary\nIS-IS Instance: 1 VRF: default\n Instance ID: 0\n System ID: 1111.1111.1001, administratively enabled\n Router ID: IPv4: 0.0.0.0\n Multi Topology disabled, not attached\n IPv4 Preference: Level 1: 115, Level 2: 115\n IPv6 Preference: Level 1: 115, Level 2: 115\n IS-Type: Level 1 and 2, Number active interfaces: 1\n Routes both IPv4 and IPv6\n LSP size maximum: Level 1: 1492, Level 2: 1492\n Interval Type Max Wait Initial Wait Hold Interval\n ----------------------- -------- ------------ -------------\n LSP generation interval 5 s 50 ms 50 ms\n SPF interval 30000 ms 300 ms 80 ms\n Current SPF hold interval(ms): Level 1: 80, Level 2: 80\n Last Level 1 SPF run 9 seconds ago\n Last Level 2 SPF run 9 seconds ago\n CSNP generation interval: 10 seconds\n Dynamic Flooding: Disabled\n Authentication mode: Level 1: None, Level 2: None\n Graceful Restart: Disabled, Graceful Restart Helper: Enabled\n Area addresses: 40\n level 1: number DIS interfaces: 0, LSDB size: 1\n Area Leader: None\n Overload Bit is not set. \n level 2: number DIS interfaces: 0, LSDB size: 1\n Area Leader: None\n Overload Bit is not set. \n Redistributed Level 1 routes: 0 limit: Not Configured\n Redistributed Level 2 routes: 0 limit: Not Configured\n\n\n\nIf IS-IS is not configured, there is no exposure to this issue.\n\n\n\n\nswitch#show isis summary\nswitch#"}],"credits":[{"lang":"en","type":"finder","value":"This issue was discovered internally by Arista and the company is not aware of any malicious uses of these issues in customer networks."}],"descriptions":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"
On affected platforms running Arista EOS with IS-IS configured, an unauthenticated attacker who can inject a specially crafted IS-IS LSP PDU can cause the legitimate LSP to be unexpectedly purged from the IS-IS link-state database. This may result in traffic loss.
"}],"value":"On affected platforms running Arista EOS with IS-IS configured, an unauthenticated attacker who can inject a specially crafted IS-IS LSP PDU can cause the legitimate LSP to be unexpectedly purged from the IS-IS link-state database. This may result in traffic loss."}],"impacts":[{"capecId":"CAPEC-272","descriptions":[{"lang":"en","value":"CAPEC-272 Protocol Manipulation"}]}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"ADJACENT_NETWORK","availabilityImpact":"HIGH","baseScore":7.4,"baseSeverity":"HIGH","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:H","version":"3.1"},"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}]},{"cvssV4_0":{"Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","Safety":"NOT_DEFINED","attackComplexity":"LOW","attackRequirements":"PRESENT","attackVector":"ADJACENT","baseScore":7,"baseSeverity":"HIGH","exploitMaturity":"NOT_DEFINED","privilegesRequired":"NONE","providerUrgency":"NOT_DEFINED","subAvailabilityImpact":"HIGH","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","userInteraction":"NONE","valueDensity":"NOT_DEFINED","vectorString":"CVSS:4.0/AV:A/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H","version":"4.0","vulnAvailabilityImpact":"HIGH","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"NONE","vulnerabilityResponseEffort":"NOT_DEFINED"},"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}]}],"problemTypes":[{"descriptions":[{"cweId":"CWE-354","description":"CWE-354: Improper Validation of Integrity Check Value","lang":"en","type":"CWE"}]}],"providerMetadata":{"dateUpdated":"2026-09-15T23:16:27.270Z","orgId":"c8b34d1a-69ae-45c3-88fe-f3b3d44f39b7","shortName":"Arista"},"references":[{"name":"Security Advisory 0160","tags":["vendor-advisory"],"url":"https://www.arista.com/en/support/advisories-notices/security-advisory/24716-security-advisory-0160"}],"solutions":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"The recommended resolution is to upgrade to a fixed software version.
"}],"value":"The recommended resolution is to upgrade to a fixed software version."}],"source":{"advisory":"0160","defects":["BUG1840507"],"discovery":"UNKNOWN"},"title":"Security Advisory 0160","workarounds":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"No workaround is available for this issue.
"}],"value":"No workaround is available for this issue."}],"x_generator":{"engine":"Vulnogram 1.0.5"}}},"cveMetadata":{"assignerOrgId":"c8b34d1a-69ae-45c3-88fe-f3b3d44f39b7","assignerShortName":"Arista","cveId":"CVE-2026-73459","datePublished":"2026-09-15T23:16:27.270Z","dateReserved":"2026-08-12T16:45:03.511Z","dateUpdated":"2026-09-16T19:34:44.583Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-09-16 00:17:05","lastModifiedDate":"2026-09-16 20:17:27","problem_types":["CWE-354","CWE-354 CWE-354: Improper Validation of Integrity Check Value"],"metrics":{"cvssMetricV40":[{"source":"psirt@arista.com","type":"Secondary","cvssData":{"version":"4.0","vectorString":"CVSS:4.0/AV:A/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H/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","baseScore":7,"baseSeverity":"HIGH","attackVector":"ADJACENT","attackComplexity":"LOW","attackRequirements":"PRESENT","privilegesRequired":"NONE","userInteraction":"NONE","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"NONE","vulnAvailabilityImpact":"HIGH","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","subAvailabilityImpact":"HIGH","exploitMaturity":"NOT_DEFINED","confidentialityRequirement":"NOT_DEFINED","integrityRequirement":"NOT_DEFINED","availabilityRequirement":"NOT_DEFINED","modifiedAttackVector":"NOT_DEFINED","modifiedAttackComplexity":"NOT_DEFINED","modifiedAttackRequirements":"NOT_DEFINED","modifiedPrivilegesRequired":"NOT_DEFINED","modifiedUserInteraction":"NOT_DEFINED","modifiedVulnConfidentialityImpact":"NOT_DEFINED","modifiedVulnIntegrityImpact":"NOT_DEFINED","modifiedVulnAvailabilityImpact":"NOT_DEFINED","modifiedSubConfidentialityImpact":"NOT_DEFINED","modifiedSubIntegrityImpact":"NOT_DEFINED","modifiedSubAvailabilityImpact":"NOT_DEFINED","Safety":"NOT_DEFINED","Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","valueDensity":"NOT_DEFINED","vulnerabilityResponseEffort":"NOT_DEFINED","providerUrgency":"NOT_DEFINED"}}],"cvssMetricV31":[{"source":"psirt@arista.com","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H","baseScore":7.4,"baseSeverity":"HIGH","attackVector":"ADJACENT_NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"CHANGED","confidentialityImpact":"NONE","integrityImpact":"NONE","availabilityImpact":"HIGH"},"exploitabilityScore":2.8,"impactScore":4}],"ssvcV203":[{"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","ssvcData":{"timestamp":"2026-09-16T19:34:28.975379Z","id":"CVE-2026-73459","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}]},"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"73459","Ordinal":"1","Title":"Security Advisory 0160","CVE":"CVE-2026-73459","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"73459","Ordinal":"1","NoteData":"On affected platforms running Arista EOS with IS-IS configured, an unauthenticated attacker who can inject a specially crafted IS-IS LSP PDU can cause the legitimate LSP to be unexpectedly purged from the IS-IS link-state database. This may result in traffic loss.","Type":"Description","Title":"Security Advisory 0160"}]}}}