Windows Volume Manager EUVD-2026-73491

Requires an existing authenticated low-privilege local user account on the target system - a standard Windows user session is sufficient. No special configuration, non-default features, or elevated starting privileges are needed. AV:L confirms the attacker must have local code execution already (physical, RDP, SSH with shell, or malware foothold). AC:L and UI:N confirm no specific timing, race condition, or victim interaction is required once local access is achieved. Exploitation is limited to the local machine (S:U, scope unchanged); no direct remote exploitation path exists without a prior initial access vector. The attack applies equally to client and server editions, including Server Core installations.

The CVSS 7.8 base score reflects realistic severity: AV:L limits the attack surface to local access, but AC:L/PR:L/UI:N means any standard user account on any unpatched Windows system is a viable launch point. This is a textbook post-exploitation or lateral-movement enabler - initial access by any means (phishing, RDP brute-force, compromised service account) is immediately followed by SYSTEM escalation. No KEV listing and no public POC are identified in the available data; however, kernel privilege escalation vulnerabilities in Windows Volume Manager are a recurring target class (e.g., similar prior CVEs in disk management drivers). EPSS data is not provided, but the ubiquitous Windows footprint and low exploitation complexity elevate operational priority despite the absence of confirmed active exploitation. The full C:H/I:H/A:H impact triad is credible for a kernel-level compromise. One data anomaly worth flagging: Windows 11 24H2 and Windows Server 2025 share build base 10.0.26100 but list different fix build numbers (9445 vs. 33438 respectively) - verify patch applicability against the Microsoft Security Update Guide directly.

An attacker who has gained a standard user foothold on a Windows endpoint - via phishing, credential stuffing against a Remote Desktop service, or compromised service account - triggers the integer overflow in the Volume Manager Driver by invoking a crafted IOCTL or system call targeting the vulnerable code path. The arithmetic wraparound causes a kernel pool allocation smaller than the data written into it, overwriting adjacent kernel structures. The attacker escalates from low-privilege user to SYSTEM and proceeds to dump credentials from LSASS or install a persistent backdoor. No public proof-of-concept is identified at time of analysis, but the low complexity and absence of user interaction make this straightforward to weaponize for an attacker with kernel exploit development capability.