CVE-2026-66307: Skype for Business and Lync Denial of Service Vulnerability
Integer underflow (wrap or wraparound) in Skype for Business allows an unauthorized attacker to deny service over a network.
Details
Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-66307
Referenced CVEs
| CVE | CSIRTS overview | External |
|---|---|---|
| CVE-2026-66307 | coverage & exploitation status | NVD · CVE.org |
Same CVEs, other sources
How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.
Recent advisories for Skype for Business
A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.
- highCVE-2026-69646: Improper verification of cryptographic signature in Skype for Business allows an unauthorized …nvd · 2026-09-08
- mediumCVE-2026-69642: Improper neutralization of input during web page generation ('cross-site scripting') in Skype …nvd · 2026-09-08
- mediumCVE-2026-66308: Out-of-bounds read in Skype for Business allows an authorized attacker to deny service over a …nvd · 2026-09-08
- highCVE-2026-66307: Integer underflow (wrap or wraparound) in Skype for Business allows an unauthorized attacker t…nvd · 2026-09-08
- mediumCVE-2026-66306: Generation of error message containing sensitive information in Skype for Business allows an u…nvd · 2026-09-08
- highCVE-2026-66305: Use of client-side authentication in Skype for Business allows an authorized attacker to perfo…nvd · 2026-09-08
More from Microsoft Security Response Center
- unknownCVE-2026-85062: Colord: Slow rejection of oversized malformed color strings2026-09-08
- mediumCVE-2026-18924: HTTP/2 server push UAF2026-09-08
- highCVE-2026-69630: Windows Win32k Elevation of Privilege Vulnerability2026-09-08
- mediumCVE-2026-80834: crypto: sun8i-ce - Remove crypto_rng interface2026-09-08
- unknownCVE-2026-83616: xmldom: Processing Instruction Target Injection Bypasses requireWellFormed2026-09-08