Vulnerability Intelligence Report
Skype for Business and Lync Denial of Service Vulnerability
CVE-2026-66307
Integer underflow (wrap or wraparound) in Skype for Business allows an unauthorized attacker to deny service over a network.
No Active Exploit Signals
CVSS Base Score
7.5
HIGH
Exploitability:3.9
Impact Score:3.6
EPSS Probability:0.63%
Executive Threat Verdict
Evaluating...
Evaluating Threat Landscape...
Assessing known weaponization, exploitation telemetry, and federal advisories.
Attack Surface
—
Authentication
—
Weaponization
—
SSVC Action
—
Weaknesses (CWE)
CWE-191 ↗CWE-191: Integer Underflow (Wrap or Wraparound)
Affected Products & Versions
| Vendor | Product | Affected Versions |
|---|---|---|
| Microsoft | Skype for Business Server 2015 CU13 | 9319.0 < 6.0.9319.885 (affected) |
| Microsoft | Skype for Business Server 2019 CU8 | 2046.0 < 7.0.2046.569 (affected) |
| Microsoft | Skype for Business Server Subscription Edition CU1 | 2046.0 < 7.0.2046.879 (affected) |
References & Technical Advisories
No reference links found.
Threat Intelligence Signals
EPSS Score
0.632%
GitHub Advisory
Identity & Timeline
| Status | PUBLISHED |
| Assigning Authority | Microsoft Corporation · Vendor · USA |
| Reserved | 2026-07-24T18:06:51 |
| Published | 2026-09-08T18:39:44 |
| Patch Date | 2026-09-08 |
| Last Updated | 2026-09-23T22:40:34 |
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