EUVD-2026-56647
GHSA-v3wj-cq6j-489r
Severity by source
AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Local attack vector and high complexity confirmed by race condition mechanics; PR:L required for initial authenticated session; full CIA impact upon successful privilege escalation.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
Lifecycle Timeline
3DescriptionCVE.org
Concurrent execution using shared resource with improper synchronization ('race condition') in Windows Telephony Service allows an authorized attacker to elevate privileges locally.
AnalysisAI
Local privilege escalation via race condition in Windows Telephony Service affects a sweeping range of Microsoft Windows client and server editions, from Server 2012 through Windows 11 26H1. An authorized local attacker with low-privileged access can exploit improper synchronization over a shared resource to elevate to higher privilege levels, achieving full confidentiality, integrity, and availability impact on the vulnerable system. No public exploit identified at time of analysis, and the vulnerability is not listed in CISA KEV; however, the breadth of affected Windows versions across enterprise environments makes unpatched exposure a meaningful operational risk.
Technical ContextAI
Windows Telephony Service implements the Windows Telephony Application Programming Interface (TAPI), providing call-control abstractions for voice and data communications on Windows systems. The root cause is CWE-362 (Concurrent Execution Using Shared Resource with Improper Synchronization), a race condition class where multiple threads or processes access a shared resource without adequate locking or synchronization primitives. This commonly manifests as a time-of-check/time-of-use (TOCTOU) issue: an attacker manipulates shared state between when a privilege check occurs and when the privileged operation executes. The CVSS vector AV:L/AC:H reflects that exploitation is local and requires precise timing control to reliably win the race window, consistent with classic TOCTOU exploitation techniques. Affected CPE targets span Windows NT 6.x through 10.x kernel families.
RemediationAI
A vendor-released patch is available and should be applied immediately via Windows Update or WSUS. Specific patched build versions confirmed by EUVD data include: Windows Server 2025 to build 10.0.26100.33296 or later, Windows 11 24H2 to 10.0.26100.9168 or later, Windows 11 25H2 to 10.0.26200.9168 or later, Windows 11 26H1 to 10.0.28000.2704 or later, Windows 11 23H2 to 10.0.22631.7517 or later, Windows Server 2022 to 10.0.20348.5499 or later, Windows 10 22H2 to 10.0.19045.7663 or later, Windows Server 2019 to 10.0.17763.9115 or later, Windows Server 2016 to 10.0.14393.9418 or later, Windows Server 2012 R2 to 6.3.9600.23337 or later, and Windows Server 2012 to 6.2.9200.26279 or later. Consult the MSRC advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-62734 for the complete patch matrix. As a compensating control where patching is not immediately feasible, consider disabling the Windows Telephony Service (TapiSrv) on systems that do not require telephony functionality - note this will break TAPI-dependent applications including some VoIP and modem software. Restrict local interactive logon and remote desktop access to only trusted, necessary accounts to limit the attacker prerequisite of low-privileged local access.
More in Windows 10 1607
View allWindows MSHTML component contains a remote code execution vulnerability that allows attackers to craft malicious ActiveX
<p>A remote code execution vulnerability exists when the Windows Print Spooler service improperly performs privileged fi
Windows MSDT (Microsoft Support Diagnostic Tool) allows remote code execution when called via the ms-msdt URL protocol f
The SMBv1 server in Microsoft Windows Vista SP2; Windows Server 2008 SP2 and R2 SP1; Windows 7 SP1; Windows 8.1; Windows
The Windows VBScript engine contains a remote code execution vulnerability in object handling that allows full system co
Windows Print Spooler Remote Code Execution Vulnerability. Rated high severity (CVSS 7.8), this vulnerability is no auth
The Win32k kernel-mode driver in Windows Vista through Windows Server 2016 allows local privilege escalation, exploited
Windows Search Remote Code Execution Vulnerability. Rated high severity (CVSS 7.5), this vulnerability is remotely explo
Denial of service against HTTP/2 server implementations allows remote unauthenticated attackers to exhaust server resour
Windows Kernel contains a TOCTOU race condition vulnerability allowing local privilege escalation, exploited by the OilR
An elevation of privilege vulnerability exists in Windows when the Win32k component fails to properly handle objects in
An elevation of privilege vulnerability exists in Windows when the Win32k component fails to properly handle objects in
Same weakness CWE-362 – Race Condition
View allSame technique Information Disclosure
View allShare
External POC / Exploit Code
Leaving vuln.today