CVE-2020-1025: Microsoft Lync

Critical severity, CVSS 9.8. EPSS: 5.9% chance of exploitation in the next 30 days.

An elevation of privilege vulnerability exists when Microsoft SharePoint Server and Skype for Business Server improperly handle OAuth token validation. An attacker who successfully exploited the vulnerability could bypass authentication and achieve improper access. To exploit this vulnerability, an attacker would need to modify the token. The update addresses the vulnerability by modifying how Microsoft SharePoint Server and Skype for Business Server validate tokens.

Affected products

• Microsoft Lync: version 2013 only
• Microsoft SharePoint Enterprise Server: version 2016 only
• Microsoft SharePoint Foundation: version 2013 only
• Microsoft SharePoint Server: version 2019 only
• Microsoft Skype For Business: version 2015 only; version 2019 only

Published 2020-07-14. Last modified 2026-06-17.