Microsoft Windows up to Server 2025 Windows Cloud Files Mini Filter Driver missing authentication

CVSS Meta Temp Score
CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.
Current Exploit Price (≈)
Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.
CTI Interest Score
Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
4.3$0-$5k0.47+

Summaryinfo

A vulnerability was found in Microsoft Windows up to Server 2025. It has been declared as problematic. This issue affects some unknown processing of the component Windows Cloud Files Mini Filter Driver. The manipulation results in missing authentication. This vulnerability is identified as CVE-2026-83991. The attack is only possible with local access. There is not any exploit available. It is best practice to apply a patch to resolve this issue.

Detailsinfo

A vulnerability classified as problematic has been found in Microsoft Windows up to Server 2025. Affected is some unknown processing of the component Windows Cloud Files Mini Filter Driver. The manipulation with an unknown input leads to a missing authentication vulnerability. CWE is classifying the issue as CWE-306. The product does not perform any authentication for functionality that requires a provable user identity or consumes a significant amount of resources. This is going to have an impact on integrity. CVE summarizes:

Missing authentication for critical function in Windows Cloud Files Mini Filter Driver allows an authorized attacker to perform tampering locally.

The advisory is available at msrc.microsoft.com. This vulnerability is traded as CVE-2026-83991 since 09/01/2026. The exploitability is told to be easy. Local access is required to approach this attack. The technical details are unknown and an exploit is not available. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 09/09/2026).

Applying a patch is able to eliminate this problem.

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Productinfo

Type

Vendor

Name

Version

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 4.4
VulDB Meta Temp Score: 4.3

VulDB Base Score: 3.3
VulDB Temp Score: 3.2
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 5.5
CNA Vector (microsoft): 🔒

CVSSv2info

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Missing authentication
CWE: CWE-306 / CWE-287
CAPEC: 🔒
ATT&CK: 🔒

Physical: Partially
Local: Yes
Remote: No

Availability: 🔒
Status: Not defined
Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Patch
Status: 🔍

0-Day Time: 🔒

Timelineinfo

09/01/2026 CVE reserved
09/09/2026 +8 days Advisory disclosed
09/09/2026 +0 days VulDB entry created
09/09/2026 +0 days VulDB entry last update

Sourcesinfo

Vendor: microsoft.com
Product: microsoft.com

Advisory: msrc.microsoft.com
Status: Confirmed

CVE: CVE-2026-83991 (🔒)
GCVE (CVE): GCVE-0-2026-83991
GCVE (VulDB): GCVE-100-401526
scip Labs: https://www.scip.ch/en/?labs.20161215

Entryinfo

Created: 09/09/2026 06:45
Changes: 09/09/2026 06:45 (63)
Complete: 🔍
Cache ID: 216::103

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