CVE tracker / CVE-2026-66305

CVE-2026-66305

CVE-2026-66305 is the Skype for Business Spoofing Vulnerability. Microsoft rates it Important, CVSS 7.1. It is not in CISA's Known Exploited Vulnerabilities catalog. Published September 8, 2026.

Risk summary

HighSpoofing
7.1
CVSS v3 base
0.5%
EPSS: chance of exploitation in 30 days
High
Severity
Important
Microsoft's rating
Less Likely
Microsoft: exploitation
No
In CISA KEV

Microsoft describes it: “Use of client-side authentication in Skype for Business allows an authorized attacker to perform spoofing over a network.”

How to fix it

Microsoft lists 3 affected products and the update that fixes each:

What Microsoft changed

Details

Weakness
CWE-603: Use of Client-Side Authentication
Publicly disclosed (Microsoft)
No
Exploited (Microsoft)
No
Known exploited (CISA KEV)
Not listed
Published
September 8, 2026
Last revised
September 8, 2026

Get told when this changes

Senserva Watch emails Microsoft security and patch alerts when something moves: a new exploitation report, a revised fix, a known issue. Free, one email address.

Join Senserva Watch

References

Microsoft Security Update Guide NVD CVE record CWE

From Microsoft, CISA, NVD and FIRST data; the Microsoft details were read when this page was opened. Check the references above before you act.