Security Flaw in Microsoft's OneDrive File Picker
Published Sources: SingCERT
What is affected, what to do
Security researchers have discovered a security flaw in the Microsoft OneDrive File Picker, which may allow third-party applications to gain full access to a user’s OneDrive storage, even when a user intends to upload a single file only. Background Security researchers have discovered a security flaw in the Microsoft OneDrive File Picker, which may allow third-party applications to gain full access to a user’s OneDrive storage, even when a user intends to upload a single file only.
The available sources name no fixed version. Check the vendor guidance in the references below.
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Metrics
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Priority
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CVSS v3
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EPSS score
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- Severity
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Priority (0–325)
The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?
Read in glossary- 9.14 Methodology
Exploit maturity
An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.
Read in glossary- no public PoC known
KEV status
The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.
Read in glossary- —
- Published
Classification under NIS2 and CRA
Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.
NIS2
NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.
Read in glossary- Handle the vulnerability in regular vulnerability handling under Art. 21(2)(e) NIS2.
CRA
The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.
Read in glossary- From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
ISO/IEC 27001
ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.
Read in glossary- Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.
Description
Security researchers have discovered a security flaw in the Microsoft OneDrive File Picker, which may allow third-party applications to gain full access to a user’s OneDrive storage, even when a user intends to upload a single file only. Background Security researchers have discovered a security flaw in the Microsoft OneDrive File Picker, which may allow third-party applications to gain full access to a user’s OneDrive storage, even when a user intends to upload a single file only. Impact Successful exploitation of the security flaw could allow a third-party application to gain unauthorised access to a user's entire cloud storage content, enabling the app to read, modify, or delete content without the user’s explicit intention, resulting in data loss and violation of compliance regulations. Affected Products The security flaw affects any application that uses the Microsoft OneDrive File Picker to request access via OAuth, including Microsoft 365 OneDrive Personal and Business accounts and applications that request OneDrive access via OAuth consent flows. Mitigation Users and administrators of the affected products are advised to review and revoke access for unnecessary or untrusted third-party applications. Organisations should also restrict OAuth app consent settings in Azure Active Directory, enable admin approval workflows, and monitor for any unusual OneDrive activity. Users should exercise caution when authorising apps that request for OneDrive access. References: https://thehackernews.com/2025/05/microsoft-onedrive-file-picker-flaw.html https://learn.microsoft.com/en-us/onedrive/developer/controls/file-pickers/?view=odsp-graph-online
Source: CSA/SingCERT