Windows Cloud Files EUVD-2026-56352

Exploitation requires an existing local authenticated session with at least standard user (low-privilege) access, as reflected by PR:L in the CVSS vector. The Windows Cloud Files Mini Filter Driver must be loaded, which is the default state on all modern Windows systems where the Cloud Files API is available (Windows 10 1809 and later). No special non-default configuration of the Cloud Files feature is indicated as a prerequisite - the driver is present by default. Exploitation is limited to local access only (AV:L); remote unauthenticated exploitation is not possible with this vector. The key limiting factor is that the attacker must already have code execution as a low-privileged user on the target system, making this a post-exploitation or insider-threat scenario rather than an initial access vector.

The CVSS 3.1 vector AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H scores 7.8, accurately reflecting a local privilege escalation requiring only a standard user account with no user interaction and low complexity. This is a realistic post-exploitation tool: an attacker who has phished credentials, exploited a remote code execution vulnerability, or compromised a service account can use this flaw to become SYSTEM. The AC:L rating indicates no race conditions or special timing is required, lowering the exploitation bar considerably. No EPSS score was provided in the input data, and the vulnerability is not listed in CISA KEV, so active widespread exploitation is not confirmed. However, the combination of low complexity, no user interaction, and coverage of all supported Windows versions elevates this beyond a theoretical risk. The patch is vendor-confirmed, so unpatched systems represent the primary exposure window. The S:U (scope unchanged) rating is consistent with a kernel driver LPE that does not inherently escape to other systems, though SYSTEM access trivially enables lateral movement.

An attacker who has gained a foothold as a low-privileged domain user - for example, via a phished credential or exploitation of a browser vulnerability - executes a crafted local process that triggers the heap-based buffer overflow in the Cloud Files Mini Filter Driver (cldflt.sys). By carefully grooming the kernel pool, the attacker corrupts a kernel object to redirect execution, achieving SYSTEM privileges and enabling them to disable endpoint defenses, dump credentials, or deploy ransomware. No public proof-of-concept code has been identified at time of analysis, but the AC:L rating indicates the exploit path does not require complex timing or environmental prerequisites.