Integer Underflow in Skype for Business Leads to DoS

Publication date: 2026-09-08

Last updated on: 2026-09-08

Assigner: Microsoft Corporation

Description

Integer underflow (wrap or wraparound) in Skype for Business allows an unauthorized attacker to deny service over a network.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-09-08

Last Modified

2026-09-08

Generated

2026-09-29

AI Q&A

2026-09-10

EPSS Evaluated

2026-09-27

NVD

CVE-2026-66307

Affected Vendors & Products

Vendor	Product	Version / Range
microsoft	skype_for_business	*

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-191	The product subtracts one value from another, such that the result is less than the minimum allowable integer value, which produces a value that is not equal to the correct result.

Attack-Flow Graph

Executive Summary

This vulnerability is an integer underflow issue in Skype for Business that allows an unauthorized attacker to disrupt service over a network. It does not require authentication or user interaction to exploit.

Impact Analysis

An attacker could exploit this to cause a denial of service, making Skype for Business unavailable for users. This could disrupt communication and collaboration in affected environments.

Mitigation Strategies

Apply the latest security updates from Microsoft for Skype for Business immediately to patch the integer underflow vulnerability. Monitor network traffic for unusual denial-of-service patterns targeting Skype for Business services.

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