Quick answers
- Is CVE-2026-20940 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-20940 being exploited in the wild.
- How severe is CVE-2026-20940?
- High severity, with a CVSS score of 7.8, published 13 January 2026.
- Which products and versions are affected?
- Microsoft Windows 11 22H3, 23H2; Microsoft Windows 10 1607, 1809, 21H2, 22H2; Microsoft Windows Server 2008 SP2, R2 SP1.
- Is there a fix for CVE-2026-20940?
- 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-2026-20940 attacked?
- It is attacked with local access, in an operating system.
- Am I affected by CVE-2026-20940?
- Check whether you run Microsoft Windows 11, Microsoft Windows 10 or Microsoft Windows Server 2008 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
A heap-based buffer overflow vulnerability exists in the Windows Cloud Files Mini Filter Driver (cldflt.sys). The flaw is categorized as an untrusted pointer dereference (CWE-822) that leads to a buffer overflow condition. An attacker with local access and low-level privileges can exploit this vulnerability by sending specially crafted requests to the driver. Successful exploitation allows the attacker to execute code with SYSTEM privileges, effectively taking full control of the affected host. Microsoft has released security updates to address this issue across various versions of Windows and Windows Server.
Affected products
- Microsoft Windows 10 1607, 1809, 21H2, 22H2
- Microsoft Windows 11 22H3, 23H2
- Microsoft Windows Server 2008 SP2, R2 SP1
Timeline
- 2026-01-13: disclosed
- 2026-01-13: advisory