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CVE-2026-50340 is a critical use‑after‑free (UAF) vulnerability in the Windows Runtime component that allows an authenticated, low‑privileged attacker to elevate privileges to SYSTEM over a network. The flaw stems from improper memory management when the Windows Runtime handles certain brokered calls between low‑integrity app containers and higher‑privilege system services.
In normal operation, the Windows Runtime (WinRT) mediates access to system resources for Universal Windows Platform (UWP) applications. When a UWP app requests a privileged operation (e.g., file access, network binding, or process creation), the Runtime Broker – a medium‑integrity service – validates the request and performs the action on behalf of the app. To do this, the broker duplicates handles from the app’s process and passes them to a privileged system service.
The vulnerability exists in the handle‑duplication logic. Specifically, when the Runtime Broker prepares a handle for use in a privileged context, it fails to properly track the lifetime of the underlying object. An attacker can craft a sequence of WinRT calls that forces the broker to free a reference to an object while a duplicate handle still points to the same memory region. After the memory is freed, the attacker can trigger a reallocation of that memory with attacker‑controlled data, causing the privileged service to operate on a corrupted object.
This UAF condition can be exploited over the network because the attack vector is network‑reachable (CVSS: AV:N). The attacker must first authenticate with low privileges (PR:L) and overcome high attack complexity (AC:H), but no user interaction is required (UI:N). Once exploited, the vulnerability grants full control over confidentiality, integrity, and availability (C:I:H/A:H) with a changed scope (S:C), meaning the compromised component affects resources beyond its original security context.
Microsoft assigned a CVSS v3.1 base score of 8.5 (High), while VulDB rates it 9.1 (Critical). The CISA ADP assessed that exploitation is currently none and not automatable, but the technical impact is total. The vulnerability affects Windows 11 24H2, 25H2, 26H1, and Windows Server 2025. It was published on July 14, 2026, and has been tracked since June 4, 2026. No public exploit is available as of this writing, but the high CVSS score and the potential for remote privilege escalation make it a prime target for threat actors.
DailyCVE Form:
Platform: ……. Windows 11/Server 2025
Version: …….. 24H2,25H2,26H1,Server2025
Vulnerability :.. Use‑after‑free (CWE‑416)
Severity: ……. Critical (CVSS 8.5‑9.1)
date: ……….. 2026‑07‑14
Prediction: ….. Patch by 2026‑08‑11
What Undercode Say:
Analytics & Telemetry
- EPSS Score: 0.02 (percentile: 42.1%) – low probability of exploitation in the next 30 days.
- CVSS v3.1 Vector: `AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H`
– CISA KEV: Not yet added. - Exploit Price Estimate: $25,000 – $100,000 (VulDB).
- CTI Interest Score: 0.00 (low current interest).
Bash Commands to Check Vulnerable Systems
Check Windows build version (affected builds: 26100, 26200, 26300, 26400+)
systeminfo | findstr /B "OS Name OS Version"
Query installed updates for any reference to CVE-2026-50340
wmic qfe list brief | findstr "50340"
Enumerate Windows Runtime components (for forensic analysis)
Get-WmiObject -Class Win32_Product | Where-Object { $_.Name -like "Windows Runtime" }
Simulate the handle duplication path (requires admin for full trace)
logman start "WinRT-Trace" -p "Microsoft-Windows-Runtime-Broker" 0xFFFFFFFF -o C:\WinRT.etl -ets
... (reproduce attack steps) ...
logman stop "WinRT-Trace" -ets
PowerShell Snippet to Detect Potential Exploitation
Check for abnormal handle duplication events in Security log (Event ID 4672, 4673)
Get-WinEvent -FilterHashtable @{LogName='Security'; ID=4672,4673} |
Where-Object { $<em>.Message -match "Runtime Broker" -or $</em>.Message -match "DuplicateHandle" }
Exploit:
To exploit CVE‑2026‑50340, an attacker with low‑privileged network access must:
1. Authenticate to the target Windows system (e.g., via SMB, RDP, or a compromised application).
2. Craft a malicious UWP app or use an existing low‑integrity process to call the Windows Runtime broker with a sequence of requests that trigger the use‑after‑free.
3. Force the broker to free a reference to a kernel object (e.g., a file handle or process token) while a duplicate handle remains alive in the attacker’s process.
4. Reallocate the freed memory with a carefully constructed fake object (e.g., a fake EPROCESS or token structure).
5. Invoke a privileged WinRT API that uses the corrupted handle, causing the system to treat the attacker’s fake object as legitimate and grant SYSTEM privileges.
The attack is network‑reachable, meaning it can be launched remotely over a LAN or WAN, provided the attacker has valid credentials. No user interaction is required, and the exploitation complexity is high due to the need for precise heap grooming and timing. As of now, no public proof‑of‑concept exists, but the vulnerability is considered easy to exploit once the internal logic is understood.
Protection:
- Apply Microsoft’s official patch as soon as it is released (expected August 2026 Patch Tuesday). Monitor the Microsoft Update Guide for CVE‑2026‑50340.
- Restrict network access to Windows Runtime broker services (port 135, 445, and dynamic RPC ports) using Windows Firewall or network segmentation.
- Enable additional authentication for remote administrative connections (e.g., require multi‑factor authentication for RDP and SMB).
- Deploy endpoint detection and response (EDR) solutions that can monitor abnormal handle duplication and privilege escalation patterns.
- Harden UWP app containers by enforcing strict app‑container policies and disabling unnecessary WinRT capabilities.
- Regularly audit security logs for Event IDs 4672 (Special Privileges Assigned) and 4673 (Privileged Service Called) originating from the Runtime Broker.
- Consider temporary mitigation by disabling the Windows Runtime Broker service if it is not essential in your environment (note: this may break many UWP applications).
Impact:
- Confidentiality: An attacker can read sensitive system files, registry hives, and memory contents of other processes, including LSASS credentials.
- Integrity: Full control over system files and registry allows installation of backdoors, rootkits, and malware.
- Availability: The attacker can crash or terminate critical system services, leading to denial‑of‑service or system instability.
- Business Risk: Systems running Windows 11 24H2/25H2/26H1 and Server 2025 are at risk. A successful exploit could lead to complete compromise of domain controllers, file servers, or critical workstations, enabling ransomware deployment, data exfiltration, or lateral movement across the network.
- Compliance: Organizations subject to GDPR, HIPAA, or PCI‑DSS may face regulatory penalties if this vulnerability is exploited and sensitive data is exposed.
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Sources:
Reported By: nvd.nist.gov
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