EUVD-2026-78203
GHSA-x5j2-9m8v-88hr
Severity by source
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
Adjacent-only access, timing-dependent race condition (AC:H), requires authenticated 802.1X supplicant (PR:L); integrity-only impact from transient unrestricted forwarding, no C or A impact.
Primary rating from Vendor (arista).
CVSS VectorVendor: arista
Lifecycle Timeline
1DescriptionCVE.org
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.
AnalysisAI
Arista EOS network switches permit an authenticated 802.1X supplicant on an adjacent Layer 2 segment to send traffic unrestricted by its assigned ACL during a brief race window - spanning milliseconds to seconds - between the completion of the authentication handshake and the point at which the switch fully enforces the authorization policy. The flaw is classified under CWE-862 (Missing Authorization) and affects all EOS releases through 4.33.7.1M as well as specific 4.34.x and 4.35.x branches. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | 802.1X port-based NAC must be configured on the affected Arista EOS switch, and the attacker must be an authenticated 802.1X supplicant - possession of valid credentials or a compliant supplicant certificate is required (PR:L). … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 4.0 base score of 2.1 (Low) is well-calibrated for this issue. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | The primary remediation is to upgrade to a fixed EOS release. … Detailed patch versions, workarounds, and compensating controls in full report. |
Threat intelligence, references, and detailed analysis are available after sign-in.
Same weakness CWE-862 – Missing Authorization
View allSame technique Authentication Bypass
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External POC / Exploit Code
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