Vulnerability · Published Sep 8, 2026 · Assigned by microsoft
CVE-2026-66307Skype for Business and Lync Denial of Service Vulnerability
High 7.5
In plain English
A high-severity security flaw in Skype for Business Server 2015 CU13 from Microsoft. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 1.2% (higher than 68% of all known vulnerabilities).
Severity (CVSS 3.1)7.5High
Exploit odds (30 days)1.2%top 32.3% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known
Official description
Integer underflow (wrap or wraparound) in Skype for Business allows an unauthorized attacker to deny service over a network.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Microsoft | Skype for Business Server 2015 CU13 | 9319.0 – before 6.0.9319.885 |
| Microsoft | Skype for Business Server 2019 CU8 | 2046.0 – before 7.0.2046.569 |
| Microsoft | Skype for Business Server Subscription Edition CU1 | 2046.0 – before 7.0.2046.879 |
Weakness: CWE-191 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C
References
- Skype for Business and Lync Denial of Service Vulnerability vendor-advisory, patch