CVE-2026-66305CWE-603

CVE-2026-66305

High · published September 8, 2026

CVSS v3.1
7.1
EPSS
1%
Percentile
43.7
In the wild
Unconfirmed
What it is

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

The record
Technical detail
CVSS v3.1
7.1 · HIGH
Vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:N
CVSS v4.0
Not supplied
EPSS
0.00526 · 43.7th percentile
Weakness
CWE-603 · Use of Client-Side Authentication
Published
2026-09-08T23:18Z
Affected products (6)
ProductVersionsFixed in
microsoft/skype_for_business_serverall versions—
microsoft/skype_for_business_serverall versions—
microsoft/skype_for_business_serverall versions—
microsoft/skype_for_business_serverall versions—
microsoft/skype_for_business_serverall versions—
microsoft/skype_for_business_server_subscription_editionall versions—
References (1)
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-66305 · [email protected]
EPSS history
Timeline
  • 10 SEP 03:17Z
    EPSS moved — → 0%
    epss
  • 08 SEP 18:32Z
    Skype for Business Spoofing Vulnerability
    cvelistv5