Quick answers
- Is CVE-2026-83991 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-83991 being exploited in the wild.
- How severe is CVE-2026-83991?
- Medium severity, with a CVSS score of 5.5, published 8 September 2026.
- Which products and versions are affected?
- Microsoft Windows Cloud Files Mini Filter Driver <UNKNOWN>.
- Is there a fix for CVE-2026-83991?
- No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
- How is CVE-2026-83991 attacked?
- It is attacked with local access.
- Am I affected by CVE-2026-83991?
- Check whether you run Microsoft Windows Cloud Files Mini Filter Driver at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
The vulnerability is an authentication bypass in a critical function within the Windows Cloud Files Mini Filter Driver. The issue is exploitable by an authorized local attacker and does not require network access or user interaction. An attacker with local system access can bypass authentication controls to tamper with driver functionality, potentially allowing unauthorized modification of cloud file handling behavior. A patch is expected to be available through Microsoft's standard security update process.
Affected products
- Microsoft Windows Cloud Files Mini Filter Driver <UNKNOWN>
Timeline
- 2026-09-08: disclosed