EUVD-2026-43870
GHSA-wxv7-999p-7wx2
Severity by source
AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Local low-privileged foothold (AV:L/PR:L) exploiting a timing-dependent race (AC:H) yields full SYSTEM compromise (C:H/I:H/A:H); scope unchanged.
Primary rating from Vendor (microsoft).
CVSS VectorNVD
Lifecycle Timeline
5DescriptionNVD
Concurrent execution using shared resource with improper synchronization ('race condition') in Windows Audio Service allows an authorized attacker to elevate privileges locally.
AnalysisAI
Local privilege escalation in the Windows Audio Service on Windows 11 (versions 24H2, 25H2, and 26H1) lets a low-privileged local user win a race condition (CWE-362) to gain full SYSTEM-level control over confidentiality, integrity, and availability. The flaw was reported by Microsoft, which has released a fix; there is no public exploit identified at time of analysis, and CISA's SSVC framework records exploitation as 'none' despite the 'total' technical impact. EPSS is low at 0.19% (9th percentile), consistent with the high attack complexity of exploiting a timing window.
Technical ContextAI
The vulnerability lives in the Windows Audio Service (audiosrv/audioendpointbuilder), a core user-facing subsystem present on all Windows 11 installations. The root cause is CWE-362, concurrent execution using a shared resource with improper synchronization - a race condition in which two threads access shared state without proper locking, allowing an attacker to interpose between a check and a use (or between resource validation and consumption). By repeatedly triggering the vulnerable code path and precisely timing operations, an attacker manipulates the shared resource into an inconsistent state that the service then acts on with its elevated privileges. The affected CPEs are cpe:2.3:a:microsoft:windows_11_version_24h2, :25h2, and :26h1, confirming the scope is limited to current Windows 11 servicing branches.
RemediationAI
Apply the Microsoft security update via Windows Update. The fixed builds are Windows 11 24H2 at 10.0.26100.8875 or later, 25H2 at 10.0.26200.8875 or later, and 26H1 at 10.0.28000.2269 or later; consult https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-50440 for the specific KB. No standalone vendor workaround is published, which is expected for an OS-service race condition - the fix is the synchronization correction in the patched binaries. As a compensating control until patching, limit interactive and local-logon rights so untrusted or low-privileged users cannot run code on the host (the flaw requires a local foothold), and prioritize patching multi-user and shared workstations where more accounts can reach the vulnerable service; note the trade-off that restricting local logon does not help on systems where standard users legitimately need interactive access.
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Same weakness CWE-362 – Race Condition
View allSame technique Information Disclosure
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External POC / Exploit Code
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