Windows Installer EUVD-2026-99488

Exploitation requires the attacker to already have authenticated, low-privileged local code execution on the target Windows system (PR:L, AV:L); it cannot be performed remotely or by an unauthenticated user. The attacker then triggers a use-after-free in the Windows Installer component to execute code at a higher privilege level. No user interaction is required (UI:N). Key limiting factors: the High attack complexity (AC:H) implies a race/timing condition that reduces reliability and may require multiple attempts, exploitation is bounded to a local foothold, and Microsoft has already published a patch across all affected builds (e.g., Windows 11 24H2 fixed in 10.0.26100.9711, Server 2025 in 10.0.26100.33650), so patched systems are not exposed.

Signals are largely consistent and point to a genuine but non-emergency local privilege-escalation issue rather than a top-priority remote threat. The CVSS 3.1 vector (AV:L/AC:H/PR:L/UI:N/S:U, C:H/I:H/A:H, base 7.0 High) describes a flaw requiring an attacker to already be a local, low-privileged, authenticated user, with high attack complexity - consistent with the race-condition nature of a use-after-free (CWE-416). CISA's SSVC framework reinforces a lower-urgency posture: Exploitation=none (no observed activity), Automatable=no (cannot be mass-reliably triggered, matching AC:H), and Technical Impact=total (full compromise once exploited, matching C:H/I:H/A:H). No EPSS score was provided in the input, and there is no KEV listing and no POC indicator, so exploitation status is 'no public exploit identified at time of analysis.' There is no conflict among the signals: a locally-scoped, high-complexity EoP with a patch available and no evidence of exploitation is a routine patch-cycle item for most environments, though its ubiquity on Windows and 'total' technical impact mean privileged/multi-user hosts should prioritize the vendor update. Note the input 'Denial Of Service' tag is somewhat at odds with the 'elevate privileges' description and C/I/A:H impact profile - the primary impact is privilege escalation, with DoS being a secondary possibility inherent to memory corruption.

A local attacker who has already obtained low-privileged code execution on a Windows host (e.g., a standard user account or a compromised low-integrity process) triggers a use-after-free condition in the Windows Installer service to corrupt memory and execute code in a higher-privileged (SYSTEM) context. Because attack complexity is High, the attacker likely must win a race condition and may need several attempts for reliable exploitation. No public exploit identified at time of analysis, and no user interaction is required once the attacker has local access.