EUVD-2026-43826
GHSA-44rq-rg9q-573c
Severity by source
AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Local access with an existing low-privileged account is required (AV:L/PR:L); the race-condition timing window makes exploitation unreliable (AC:H); successful EoP yields full local compromise (C:H/I:H/A:H).
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Lifecycle Timeline
2DescriptionCVE.org
Concurrent execution using shared resource with improper synchronization ('race condition') in Windows AppX Deployment Service allows an authorized attacker to elevate privileges locally.
AnalysisAI
Local privilege escalation in the Windows AppX Deployment Service (AppXSvc) lets an already-authenticated, low-privileged user win a race condition to elevate to higher privileges across a broad range of Windows client and server builds (Windows 10 1607 through Windows 11 26H1, and Windows Server 2012 through 2025). The flaw stems from improper synchronization of a shared resource, and successful exploitation yields full confidentiality, integrity, and availability impact on the host. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires the attacker to already be an authenticated, low-privileged local user on the target host (CVSS PR:L, AV:L) and to interact with the Windows AppX Deployment Service (AppXSvc) - the component that installs/updates packaged MSIX/AppX applications - so the concrete prerequisite is the ability to invoke or influence a package-deployment operation. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 3.1 base score is 7.0 (High) with vector AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H, meaning local access and existing low privileges are required, exploitation is of high attack complexity, and no user interaction is needed while impact is total (C:H/I:H/A:H). … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker who already holds a low-privileged foothold on a Windows host (for example a compromised standard user account or a low-privilege service) runs a small program that repeatedly triggers an AppX/MSIX deployment operation while manipulating a shared resource. By winning the timing window in the AppX Deployment Service, the attacker causes a privileged action to operate on attacker-controlled state and elevates to higher privileges. … |
| Remediation | Apply the Microsoft security update for CVE-2026-49803, delivered through the monthly cumulative update for each affected build (Patch available per vendor advisory); the specific KB and fixed build number should be taken directly from the MSRC advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-49803, since an exact fix version is not included in the provided data. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours: Inventory all Windows systems across client (Windows 10, 11) and server (2012-2025) editions and prioritize business-critical infrastructure and devices accessed by administrative or privileged users; confirm patch availability from Microsoft security advisories. …
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External POC / Exploit Code
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