Sep 2026: Skype for Business Spoofing Vulnerability
CVE-2026-66305 Published on September 8, 2026
Skype for Business Spoofing Vulnerability
Use of client-side authentication in Skype for Business allows an authorized attacker to perform spoofing over a network.
Weakness Type
Use of Client-Side Authentication
A client/server product performs authentication within client code but not in server code, allowing server-side authentication to be bypassed via a modified client that omits the authentication check. Client-side authentication is extremely weak and may be breached easily. Any attacker may read the source code and reverse-engineer the authentication mechanism to access parts of the application which would otherwise be protected.
Products Associated with CVE-2026-66305
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Affected Versions
Microsoft Skype for Business Server 2015 CU13:- Version 9319.0 and below 6.0.9319.885 is affected.
- Version 2046.0 and below 7.0.2046.569 is affected.
- Version 2046.0 and below 7.0.2046.879 is affected.