Microsoft Lync/Skype for Business Server/SharePoint OAuth Token privileges management

Summaryinfo

A vulnerability has been found in Microsoft Lync, Skype for Business Server and SharePoint and classified as critical. Impacted is an unknown function of the component OAuth Token Handler. Performing a manipulation results in privileges management. This vulnerability is known as CVE-2020-1025. Remote exploitation of the attack is possible. No exploit is available. Applying a patch is the recommended action to fix this issue.

Detailsinfo

A vulnerability was found in Microsoft Lync, Skype for Business Server and SharePoint (Groupware Software) (the affected version unknown). It has been classified as critical. This affects an unknown part of the component OAuth Token Handler. The manipulation with an unknown input leads to a privileges management vulnerability. CWE is classifying the issue as CWE-269. The product does not properly assign, modify, track, or check privileges for an actor, creating an unintended sphere of control for that actor. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

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.

The weakness was published 07/14/2020 as confirmed security update guide (Website). The advisory is shared at portal.msrc.microsoft.com. The public release has been coordinated with Microsoft. This vulnerability is uniquely identified as CVE-2020-1025. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Neither technical details nor an exploit are publicly available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 02/23/2026). MITRE ATT&CK project uses the attack technique T1068 for this issue. The advisory points out:

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.

Applying a patch is able to eliminate this problem. A possible mitigation has been published immediately after the disclosure of the vulnerability.

If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Productinfo

Type

• Groupware Software

Vendor

• Microsoft

Name

• Lync
• SharePoint
• Skype for Business Server

License

• commercial

Website

• Vendor: https://www.microsoft.com/

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