Windows App Store EUVD-2026-43977

Exploitation requires the attacker to already hold an authenticated local foothold on the affected host (CVSS PR:L, AV:L) - there is no remote or network path. The attacker must be able to execute code or invoke the Windows App Store / AppX component locally; no victim user interaction is needed (UI:N) and no special non-default configuration is called out, since the Store component is present by default across all listed SKUs. Limiting factors: the attacker needs valid low-privilege credentials and local access, the payoff is disclosure of memory contents rather than direct code execution, and on Server Core or hardened servers where the Store is disabled the interactive attack surface is reduced.

The provided CVSS 3.1 vector (AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N, base 7.1) indicates a locally-exploitable flaw requiring low privileges and no user interaction, which is realistic for an inbox Store component that any authenticated user can invoke. However, there is a notable internal inconsistency: the description characterizes the impact purely as information disclosure, yet the input vector asserts I:H (high integrity impact) - for a use-of-uninitialized-resource disclosure bug, an integrity impact of High is not obviously justified and should be verified with the vendor; the true impact is most consistent with confidentiality-only (C:H/I:N). No EPSS score, SSVC decision, or KEV entry was provided; the vulnerability is not in CISA KEV and no POC was reported, so there is no evidence of active or widespread exploitation. Net assessment: a legitimate patch-worthy local info-leak, useful primarily as a secondary primitive in a privilege-escalation or sandbox-escape chain, but not an emergency remote threat - prioritize in normal Patch Tuesday cadence rather than out-of-band.

A low-privileged but authenticated user on a shared Windows workstation or Remote Desktop server invokes the vulnerable Store/AppX code path, causing it to operate on an uninitialized buffer and return leftover memory contents. The attacker reads sensitive residual data - potentially credentials, tokens, or pointers useful for defeating ASLR - and uses it to advance a broader local privilege-escalation chain. No public POC has been reported, and exploitation requires local access, so the attacker must already have a foothold.