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CVE-2026-50348 is a race condition vulnerability in the Windows Runtime (WinRT) component that allows an unauthorized attacker to elevate privileges over a network. The flaw stems from improper synchronization when concurrent threads access a shared resource—specifically, the inter-process communication (IPC) mechanism used by WinRT to broker requests between low‑privileged client processes and high‑privileged system services.
At the core of the issue lies the way Windows Runtime handles handle duplication and impersonation. When a low‑integrity process requests a service from a privileged WinRT host (such as `svchost.exe` loading shsvcs.dll), the server accepts a handle to a resource owned by the client—for example, a thread, process, or access token. The server then calls `OpenProcess()` to obtain a reference to the client process and `DuplicateHandle()` to create a copy of the client’s handle that is valid within the server’s own highly privileged context.
Because the server runs with full administrative rights, any handle duplicated into its context inherits those elevated permissions. The race condition occurs when an attacker can time the duplication operation such that the server’s security context is not properly restricted before the handle is used. In a vulnerable system, the server does not call `CoImpersonateClient()` before performing the duplication; this function would temporarily lower the server’s privileges to match those of the calling client. Without this impersonation step, the duplicated handle remains bound to the server’s administrative token, effectively granting the client the ability to execute arbitrary code with SYSTEM-level privileges.
The attack vector is network‑based, meaning an attacker can send specially crafted WinRT messages to a remote machine, triggering the race. Successful exploitation requires the attacker to have low‑privileged access to the target system (e.g., through a compromised user account) and the ability to repeatedly invoke the vulnerable API to win the race condition. Once the race is won, the attacker can escalate to full system privileges, install programs, view/change/delete data, or create new accounts with administrative rights.
Microsoft addressed this vulnerability in the July 2026 Patch Tuesday release by modifying the handle duplication routine. The patch inserts a call to `CoImpersonateClient()` before `OpenProcess()` and DuplicateHandle(), ensuring that any handle duplicated into the server’s context is restricted to the client’s permission set. After the operation completes, `CoRevertToSelf()` restores the server’s original privileges. This simple but critical synchronization fix eliminates the race window and prevents privilege escalation.
DailyCVE Form:
Platform: Windows Runtime
Version: 10/11/Server 2019
Vulnerability: Race Condition
Severity: High (7.0)
Date: 2026-07-14
Prediction: Already Patched
What Undercode Say
Analytics
- CVSS v3.1 Score: 7.0 (High) – Vector: AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
- CVSS v4.0 Score: 8.7 (High) – Vector: AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
- EPSS: Not yet available (as of July 2026)
- CWE: CWE-362 (Race Condition) and CWE-416 (Use After Free)
- Exploitation: None reported in the wild; automatable: no
- Affected Products: Windows 10 v1809/21H2/22H2, Windows 11 v24H2/25H2/26H1, Windows Server 2019/2022/2025
Bash Commands to Check for Vulnerability
Check Windows version and build number systeminfo | findstr /B /C:"OS Name" /C:"OS Version" Verify if the patch (KB5012345 – hypothetical) is installed wmic qfe list brief | findstr "KB5012345" Query the registry for WinRT component version reg query "HKLM\SOFTWARE\Microsoft\Windows Runtime" /v Version Check shsvcs.dll file version (affected component) dir /a C:\Windows\System32\shsvcs.dll | findstr "shsvcs"
Exploit
An attacker with low‑privileged access to a target system crafts a malicious WinRT application that repeatedly invokes the vulnerable IPC endpoint. The application sends a handle to a thread it controls, then races the server’s duplication routine against a concurrent operation that modifies the handle’s security attributes. By winning the race, the attacker causes the privileged server to duplicate the handle with SYSTEM permissions. The attacker then resumes the duplicated thread, which now executes arbitrary shellcode with full administrative rights, effectively compromising the entire host.
Protection
- Apply the July 2026 Patch Tuesday update immediately (all supported Windows versions have received the fix).
- Enable Windows Defender Exploit Guard – specifically, the “Protect against privilege escalation” rule to block abnormal handle duplication attempts.
- Restrict network access to WinRT services using Windows Firewall or host‑based IPS to limit exposure.
- Monitor Event Logs for Event ID 4624 (successful logon) and 4672 (special privileges assigned) to detect unexpected privilege elevation patterns.
- Implement Application Control (e.g., Windows Defender Application Control) to prevent untrusted applications from invoking WinRT APIs.
Impact
Successful exploitation allows an unauthorized remote attacker to elevate privileges to SYSTEM on the target machine. This can lead to complete compromise of the system, including:
– Installation of persistent backdoors and malware.
– Exfiltration or corruption of sensitive data (credentials, documents, encryption keys).
– Creation of new administrative accounts for lateral movement within the network.
– Disablement of security controls (antivirus, EDR, firewalls) to evade detection.
Given the network‑based attack vector, this vulnerability poses a significant risk to enterprise environments where Windows Runtime is widely used for modern applications and services.
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Sources:
Reported By: nvd.nist.gov
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