---
id: CVE-2026-66305
title: >-
  Use of client-side authentication in Skype for Business allows an authorized
  attacker to perform spoofing over a network.
summary: >-
  Use of client-side authentication in Skype for Business allows an authorized
  attacker to perform spoofing over a network.
severity: high
cvss: 7.1
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:N'
cwe:
  - CWE-603
vendor: microsoft
product: skype_for_business_server
affected:
  - skype_for_business_server = 2015
  - skype_for_business_server = 2019
  - skype_for_business_server_subscription_edition = 7.0.2046.849
published: '2026-09-08'
updated: '2026-09-16'
sourceUpdated: '2026-09-16T19:24:00.377'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-66305'
references:
  - url: 'https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-66305'
    label: secure@microsoft.com
tags:
  - nvd
  - cve.org
epss: 0.00526
epssPercentile: 0.4207
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-09-09T15:49:58.190621Z'
ingestedAt: '2026-09-08T19:08:49.637Z'
---

## Overview

Use of client-side authentication in Skype for Business allows an authorized attacker to perform spoofing over a network.

## Affected

- `skype_for_business_server = 2015`
- `skype_for_business_server = 2019`
- `skype_for_business_server_subscription_edition = 7.0.2046.849`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.