# CVE-2026-77191 — Arista Networks EOS

> As of 2026-09-15, CVE-2026-77191 is a LOW-severity vulnerability in Arista Networks EOS, CVSS v3.1 2.6, EPSS 0.1% (3.7th percentile). No Threadlinqs-tracked threat campaign has been attributed to CVE-2026-77191 as of 2026-09-15; the identifier is re-checked against the Threadlinqs threat corpus on every daily ingest.

**Last updated:** 2026-09-15

## What is CVE-2026-77191?

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.

The record classifies CVE-2026-77191 under weakness class [CWE-862](https://intel.threadlinqs.com/cwe/CWE-862). Its CVSS v3 base vector states that the flaw is reachable from an adjacent network, needs low-privilege credentials, needs no user interaction. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 21 days ago.

## Severity and exploitation probability

- **CVSS v3.1 base score:** 2.6 — LOW (`CVSS:3.1/AV:A/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N`)
- **CVSS v4.0 base score:** 2.1 (`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`)
- **EPSS (FIRST):** 0.1% probability of exploitation in the next 30 days, higher than 3.7% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 1.4/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-09-14, last modified 2026-09-15

## Is CVE-2026-77191 being exploited?

It currently carries a trending score of 31 in the Threadlinqs vulnerability feed.

## Affected products and versions

- [Arista Networks](https://intel.threadlinqs.com/vendors/arista-networks): EOS

## How to fix CVE-2026-77191

No vendor patch reference has been recorded for CVE-2026-77191 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

## Threat activity tracking CVE-2026-77191

No threat campaign in the Threadlinqs corpus currently references CVE-2026-77191, in its CVE list or as an indicator. The linkage is recomputed from the live corpus on every daily ingest, so this section fills in as soon as a tracked campaign cites the identifier.

## Sources

Enriched from CVE.org, NVD, FIRST EPSS. Last verified by Threadlinqs on 2026-09-15. This product uses the NVD API but is not endorsed or certified by the NVD.

**Other references**

- [arista.com](https://www.arista.com/en/support/advisories-notices/security-advisory/24706-security-advisory-0150)

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-77191
Full detection coverage and IOCs for threats exploiting CVE-2026-77191 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp