CVE-2026-50405 Overview
CVE-2026-50405 is a local privilege escalation vulnerability in the Windows Filtering Platform (WFP). The flaw stems from insufficient granularity of access control [CWE-1220] within WFP, allowing an authorized local attacker to elevate privileges on affected systems. Microsoft has published an advisory covering all currently supported Windows client and server editions, including Windows 10, Windows 11 (24H2, 25H2, 26H1), and Windows Server 2012 through 2025. Successful exploitation grants an attacker high impact to confidentiality, integrity, and availability of the compromised host.
Critical Impact
An authenticated local attacker can escalate to higher privileges on affected Windows systems by abusing weak access control checks in the Windows Filtering Platform kernel component.
Affected Products
- Microsoft Windows 10 (1607, 1809, 21H2, 22H2)
- Microsoft Windows 11 (24H2, 25H2, 26H1)
- Microsoft Windows Server 2012, 2012 R2, 2016, 2019, 2022, and 2025
Discovery Timeline
- 2026-07-14 - CVE-2026-50405 published to NVD
- 2026-07-20 - Last updated in NVD database
Technical Details for CVE-2026-50405
Vulnerability Analysis
The Windows Filtering Platform is a set of API and system services that provide a platform for creating network filtering applications. WFP operates across user-mode and kernel-mode components and enforces filters over network traffic, connections, and socket operations. The vulnerability arises because WFP does not apply access controls at a sufficiently granular level. An authorized user who can interact with WFP interfaces can perform operations that should be restricted to more privileged callers.
Exploitation requires local access and low privileges, but no user interaction. Once triggered, the attacker gains SYSTEM-level control over the host. This class of flaw is typically chained after initial access, such as a phishing payload or an exploited service, to move from a standard user context to full kernel-level authority.
Root Cause
The root cause is classified under [CWE-1220] Insufficient Granularity of Access Control. WFP object or filter operations do not distinguish between privilege tiers with adequate precision. Callers permitted to perform benign operations gain implicit access to sensitive controls that should require SYSTEM or administrator context.
Attack Vector
The attack vector is local. The attacker must already have code execution and a valid session on the target. Exploitation involves invoking WFP APIs or IOCTLs from a low-privilege process to manipulate filter state, callouts, or associated kernel objects in ways that bypass intended privilege boundaries and yield elevated execution.
No public proof-of-concept code or exploit modules are available at the time of publication. Refer to the Microsoft CVE-2026-50405 Advisory for authoritative technical details.
Detection Methods for CVE-2026-50405
Indicators of Compromise
- Unexpected creation or modification of WFP filters, callouts, or providers by non-SYSTEM processes.
- Standard user processes spawning child processes running as NT AUTHORITY\SYSTEM shortly after interacting with fwpuclnt.dll or BFE service interfaces.
- Anomalous loading of WFP-related modules by unsigned or unusual binaries.
Detection Strategies
- Monitor process integrity level transitions where a Medium or Low integrity process yields a High or System integrity child.
- Track API calls to FwpmFilterAdd0, FwpmCalloutAdd0, and related WFP management functions originating from non-administrative processes.
- Correlate Base Filtering Engine (BFE) service events with process ancestry to identify suspicious callers.
Monitoring Recommendations
- Enable Windows kernel and Sysmon logging for process creation, image load, and access token changes.
- Forward Windows Security and BFE service logs to a centralized analytics platform for behavioral baselining.
- Alert on rare parent-child process pairs that culminate in SYSTEM-level execution.
How to Mitigate CVE-2026-50405
Immediate Actions Required
- Apply the Microsoft security update for CVE-2026-50405 to all affected Windows client and server systems.
- Prioritize patching on multi-user hosts, jump servers, and RDP-accessible endpoints where local access is more likely.
- Audit accounts with interactive logon rights and remove unnecessary local access.
Patch Information
Microsoft has released fixes through the standard security update channels. Consult the Microsoft CVE-2026-50405 Advisory for the specific KB articles corresponding to each affected Windows build and apply them via Windows Update, WSUS, or your patch management system.
Workarounds
- No official workaround has been published by Microsoft. Applying the security update is the recommended remediation.
- Enforce least-privilege policies and restrict local logon to trusted users to reduce the attacker population able to reach the vulnerable code path.
- Constrain application execution using AppLocker or Windows Defender Application Control to limit untrusted binaries that could invoke WFP APIs.
# Verify installed updates on a Windows host (PowerShell)
Get-HotFix | Sort-Object -Property InstalledOn -Descending | Select-Object -First 20
# Trigger update scan and install available patches via Windows Update
UsoClient StartScan
UsoClient StartDownload
UsoClient StartInstall
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
