CVE-2026-50339 Overview
CVE-2026-50339 is an information disclosure vulnerability in the Windows Push Notifications component. An authenticated local attacker can exploit the flaw to read sensitive information they should not be able to access. The issue is tracked under CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor) and affects a broad range of Windows client and server releases. Microsoft published the advisory in its Security Update Guide and rates confidentiality impact as high while integrity and availability remain unaffected.
Critical Impact
An authorized local attacker can disclose sensitive information handled by the Windows Push Notifications service without requiring user interaction.
Affected Products
- Microsoft Windows 10 (1809, 21H2, 22H2) on x86, x64, and ARM64
- Microsoft Windows 11 (24H2, 25H2, 26H1) on x64 and ARM64
- Microsoft Windows Server 2019, Server 2022, and Server 2025
Discovery Timeline
- 2026-07-14 - CVE-2026-50339 published to NVD
- 2026-07-20 - Last updated in NVD database
Technical Details for CVE-2026-50339
Vulnerability Analysis
The vulnerability resides in the Windows Push Notifications service, which brokers toast and raw notifications between applications and the operating system. The service handles data on behalf of multiple users and applications, so improper isolation can expose information across trust boundaries. Microsoft classifies the flaw as an information disclosure issue with high confidentiality impact and no integrity or availability effect.
Exploitation requires an attacker to already hold valid credentials on the target host. The attack executes entirely on the local machine, with no network reach and no user interaction. Successful exploitation leaks sensitive data the attacker would not otherwise be able to read, which can support follow-on activity such as credential harvesting or privilege escalation chains.
Root Cause
The root cause is inadequate protection of sensitive information processed by the Windows Push Notifications subsystem, consistent with CWE-200. Data intended for one security context becomes readable by an unauthorized actor operating in another context on the same system. Microsoft has not published low-level technical details, and no public proof-of-concept exploit is available.
Attack Vector
The attack vector is local. An authenticated user runs code or issues requests against the Push Notifications service to retrieve information belonging to other users or higher-privileged components. Because the flaw does not require user interaction, it is well suited for post-exploitation reconnaissance by malware or interactive attackers who already have a foothold.
No verified exploit code is available. Refer to the Microsoft CVE-2026-50339 Update Guide for authoritative technical details as they are released.
Detection Methods for CVE-2026-50339
Indicators of Compromise
- No public indicators of compromise have been published for CVE-2026-50339 at this time.
- Monitor Microsoft advisories and vendor threat intelligence feeds for updates as details emerge.
Detection Strategies
- Baseline normal interactions with the Windows Push Notification User Service (WpnUserService) and Windows Push Notifications System Service (WpnService) and alert on anomalous access patterns.
- Flag unexpected processes that enumerate notification databases under %LOCALAPPDATA%\Microsoft\Windows\Notifications\ (for example, wpndatabase.db).
- Alert on unusual cross-user access attempts to per-user notification storage locations.
Monitoring Recommendations
- Enable Windows security auditing for object access on notification-related files and registry keys.
- Forward endpoint telemetry, including process creation and file access events, into a centralized data lake for correlation.
- Review installed patch levels across Windows 10, Windows 11, and Windows Server fleets to identify hosts missing the fix.
How to Mitigate CVE-2026-50339
Immediate Actions Required
- Apply the Microsoft security update referenced in the CVE-2026-50339 advisory to all affected Windows client and server systems.
- Prioritize multi-user hosts such as Remote Desktop Session Hosts, VDI infrastructure, and shared workstations where local access is more common.
- Audit local account membership and remove unnecessary interactive logon rights.
Patch Information
Microsoft has issued a security update covering all listed Windows 10, Windows 11, and Windows Server versions. Consult the Microsoft CVE-2026-50339 Update Guide for the specific KB article and build numbers that apply to each product and architecture.
Workarounds
- Microsoft has not documented an official workaround; installing the security update is the recommended remediation.
- Restrict local logon and reduce the number of standard users on sensitive systems to limit the attacker population.
- Enforce least-privilege application design so notifications do not carry secrets such as credentials or tokens.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
