CVE-2026-50509: Windows WWAN Service Privilege Escalation

CVE-2026-50509 Overview

CVE-2026-50509 is a local privilege escalation vulnerability in the Windows Wireless Wide Area Network (WWAN) Service. The flaw stems from deserialization of untrusted data [CWE-502]. An authorized local attacker can exploit the service to elevate privileges on the affected Windows host. Microsoft published the advisory on July 14, 2026, and assigned a CVSS v3.1 score of 7.8. Successful exploitation grants high impact to confidentiality, integrity, and availability. No public proof-of-concept exploit has been observed, and the vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog.

Critical Impact
An authenticated local attacker can gain SYSTEM-level privileges by sending crafted serialized data to the WWAN Service.

Affected Products

Microsoft Windows (Wireless WAN Service component)
Refer to the Microsoft CVE-2026-50509 Advisory for the complete list of affected builds
Systems with the WWAN AutoConfig service (WwanSvc) enabled

Discovery Timeline

2026-07-14 - CVE-2026-50509 published to NVD
2026-07-15 - Last updated in NVD database

Technical Details for CVE-2026-50509

Vulnerability Analysis

The Windows Wireless Wide Area Network Service (WwanSvc) manages mobile broadband connections, including cellular data adapters. The service accepts serialized objects through inter-process communication channels available to authenticated local users. Because the service does not validate the type or contents of serialized input before reconstruction, an attacker can supply a crafted object graph that triggers unintended code paths during deserialization.

When the malicious object is deserialized, the process runs under a privileged security context associated with the service. The result is arbitrary code execution at the elevated privilege level. This class of flaw maps to CWE-502, Deserialization of Untrusted Data, and follows a well-documented pattern in Windows service components.

The EPSS model estimates a 2.31% probability of exploitation within 30 days, placing the CVE in the 81st percentile of scored vulnerabilities. Exploitation requires prior local access and valid low-privileged credentials, which limits mass exploitation but is realistic in post-compromise scenarios.

Root Cause

The root cause is the acceptance of untrusted serialized data by the WWAN Service without enforcing an allowlist of expected types. Deserialization instantiates arbitrary objects and executes constructors or callbacks that the attacker chooses. No cryptographic integrity check or type filter blocks the malicious payload.

Attack Vector

An attacker with local access and low-privileged credentials submits a crafted serialized payload to an IPC endpoint exposed by WwanSvc. The service deserializes the payload in its own process context, executing attacker-controlled logic with the privileges of the service account. The attacker uses this execution to install persistence, disable defenses, or move laterally.

No public exploit code is currently available. Readers requiring technical detail should review the Microsoft CVE-2026-50509 Advisory.

Detection Methods for CVE-2026-50509

Indicators of Compromise

Unexpected child processes spawned by svchost.exe hosting the WwanSvc service
New services, scheduled tasks, or persistence artifacts created shortly after WWAN Service activity
Local user accounts performing IPC calls to the WWAN Service outside normal cellular connection workflows

Detection Strategies

Monitor process creation events where svchost.exe running WwanSvc spawns interpreters such as cmd.exe, powershell.exe, or rundll32.exe
Alert on token manipulation or privilege assignment events (Windows Event IDs 4672, 4673) tied to the WWAN Service process
Correlate low-privileged user sessions with subsequent SYSTEM-level activity on the same host

Monitoring Recommendations

Enable process creation auditing with command-line logging (Event ID 4688) across Windows endpoints
Forward Sysmon telemetry, including process access and named pipe events, to a central analytics platform
Review service configuration changes and unexpected loads of unusual DLLs inside WwanSvc

How to Mitigate CVE-2026-50509

Immediate Actions Required

Apply the Microsoft security update referenced in the Microsoft CVE-2026-50509 Advisory to all Windows systems
Prioritize patching on endpoints and servers that host mobile broadband adapters or run the WWAN Service by default
Audit local account usage and remove unnecessary interactive logon rights on high-value hosts

Patch Information

Microsoft has released fixes through its standard Patch Tuesday channel. Consult the Microsoft CVE-2026-50509 Advisory for exact KB article numbers and applicable Windows builds. Deploy the update through Windows Update, WSUS, Microsoft Intune, or Configuration Manager according to standard change control.

Workarounds

Disable the WWAN AutoConfig service (WwanSvc) on systems that do not use cellular broadband hardware
Restrict local logon rights and enforce least-privilege on standard user accounts
Apply application control policies to prevent unauthorized binaries from executing under service contexts

bash

# Disable the WWAN AutoConfig service on hosts without cellular hardware
sc.exe config WwanSvc start= disabled
sc.exe stop WwanSvc