CVE-2026-85826

7.0High

Published 13 Oct 2026 · NVD status: Undergoing Analysis · AI triage by gemini-3.8-flash

7.0High

Attack vector: Local
Complexity: High
Privileges needed: Low
User interaction: None
Impact: Full C/I/A compromise
Weakness: CWE-787

Impact

A local attacker with an existing account can gain elevated system privileges. They need local access and must win a race or satisfy complex conditions against the file system driver.

Root cause

An out-of-bounds write flaw exists in the Windows Fast FAT Driver (fastfat.sys).

Affected systems

Versions not listed — check the vendor advisory.

CVSS v3.1 · CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

Fix & remediation

Install the latest Microsoft security update addressing CVE-2026-85826 via Windows Update or WSUS. If patching cannot happen immediately, restrict unprivileged local user access or block mounting of untrusted FAT/FAT32 filesystems.

AI-suggested. Run it in staging first and check it against the vendor advisory. Why?

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NVD description

Out-of-bounds write in Windows Fast FAT Driver allows an authorized attacker to elevate privileges locally.

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-85826

Source: nvd.nist.gov/vuln/detail/CVE-2026-85826