Windows Volume Manager CVE-2026-77904

The attacker must have a valid, low-privilege authenticated session on the target Windows system (PR:L in the CVSS vector). No elevation, no special group membership, and no non-default configuration is required beyond that local authenticated foothold - the CVSS AC:L rating confirms no additional preconditions. Exploitation is strictly local (AV:L); remote unauthenticated exploitation is not possible without a separate initial-access vector. No user interaction is required once the attacker has their session. Limiting factors: physical or logical local access is required, making this a second-stage exploitation primitive rather than an entry point; patching eliminates the vulnerability entirely.

With a CVSS 7.8 and AV:L/PR:L, this is a classic local privilege escalation (LPE) kernel driver flaw - high severity but not remotely triggerable on its own. No public exploit code exists and it is not listed in CISA KEV, so opportunistic mass exploitation is unlikely at this time. The practical threat model is chained exploitation: an adversary who gains initial foothold via phishing, a remote exploit, or stolen credentials at low privilege uses this flaw to escalate to SYSTEM, enabling credential dumping, lateral movement, or ransomware deployment. The extraordinary breadth of affected versions - covering every major Windows release from Server 2012 to the newest 26H1 builds - means the attack surface is effectively every unpatched Windows environment in production. Even a moderately-sized enterprise IT team should treat this as urgent patching work given the low complexity (AC:L) of exploitation once local access is obtained. EPSS data is absent from the provided intelligence, but the combination of kernel LPE, AC:L, and Microsoft's own security reporting (via secure@microsoft.com) warrants prioritizing this patch in the next maintenance cycle.

An attacker who has obtained a standard (low-privilege) local user account - through phishing, credential theft, or exploitation of an initial access vulnerability - crafts a specially formatted volume management request that triggers the heap buffer overflow in the Volume Manager Extension Driver, enabling arbitrary kernel-mode code execution and escalation to SYSTEM. No public proof-of-concept exists at time of analysis, but the AC:L rating indicates the flaw is straightforward to exploit once local access is established, making it a high-value post-exploitation link in ransomware and APT kill chains.