CVE-2026-42906

What it actually does

This is a local information disclosure vulnerability in Windows Shell. A low-privileged, already authenticated local attacker can cause Windows Shell to expose sensitive information that should not be accessible to that user. The vulnerability does not provide remote code execution, privilege escalation, integrity modification, or denial of service by itself, but it may disclose high-value local information that can support follow-on compromise.

Why it matters to the business

Successful exploitation could allow a user or malware already running on a Windows workstation or server to access sensitive local information, potentially exposing credentials, file metadata, user activity, configuration details, or other data that could help an attacker move further into the environment. The CVSS score is moderate and EPSS is currently low with no known exploitation or CISA KEV listing, but affected Windows 10, Windows 11, Windows Server 2022, and Windows Server 2025 systems are broadly deployed, so patching should be included in normal Windows security update cycles.

How an attack unfolds

An attacker first needs local authenticated access to an affected Windows system, either through a legitimate low-privileged account, malware running in a user context, or prior compromise by another technique. The attacker then invokes or manipulates Windows Shell functionality in a way that triggers the information exposure condition. If successful, Windows Shell returns or reveals sensitive information that the attacker should not be able to read. The attacker can then use the disclosed information to improve situational awareness, identify valuable files or users, harvest clues for credential theft, or support additional lateral movement or privilege escalation attempts using separate vulnerabilities or misconfigurations.

How to fix it

Apply the Microsoft security update that addresses this vulnerability on all affected Windows versions, using the latest cumulative update available for each supported release. Prioritize Windows 10 21H2 and 22H2, Windows 11 23H2, 24H2, 25H2, and 26H1, Windows Server 2022, and Windows Server 2025 systems. Where immediate patching is not possible, reduce exposure by enforcing least privilege, preventing untrusted users from interactive logon to shared systems, limiting local administrative access, hardening endpoint controls, and monitoring for suspicious local discovery or data access activity. No product-specific fixed build numbers were provided in the input, so use Microsoft Update, Windows Update for Business, WSUS, Intune, SCCM, or the Microsoft Update Catalog to deploy the applicable cumulative security update for the affected operating system branch.

How to confirm the fix worked

Confirm that each affected host has installed the cumulative Windows security update that includes the fix for this vulnerability. Validate through centralized patch management reporting, Windows Update history, Microsoft Defender Vulnerability Management, authenticated vulnerability scanning, or PowerShell inventory of installed hotfixes and OS build numbers. For scanners, ensure the plugin or detection content is current enough to recognize the June 2026 advisory and the corrected Windows build levels. Also verify that unsupported or end-of-servicing Windows builds are either upgraded to supported releases or otherwise isolated, because they may not receive a complete security fix.

Typical attack path

1. Obtain local authenticated access to an affected Windows 10, Windows 11, Windows Server 2022, or Windows Server 2025 system.
2. Run code or commands in the context of a low-privileged local user.
3. Interact with vulnerable Windows Shell functionality to trigger unauthorized information disclosure.
4. Collect the exposed sensitive information from the local system.
5. Use the disclosed information to support follow-on actions such as credential discovery, local reconnaissance, lateral movement planning, or chaining with another vulnerability.

How to detect it

Because this vulnerability is a local information disclosure issue and no public exploit maturity, known exploitation, threat actor attribution, or exploit-specific artifacts were provided, detection should focus on behavioral evidence rather than fixed signatures. Review Windows Security logs, Sysmon or EDR telemetry, PowerShell logs, process creation events, file access telemetry, and endpoint alerts around users or processes that had local access before patching. Look for unusual Windows Shell activity, unexpected child processes spawned from shell components, suspicious local reconnaissance, access to sensitive profile or system locations by non-administrative users, credential discovery behavior, and execution by unfamiliar binaries in user-writable directories. Useful log sources include Windows Security event logs, Sysmon Event ID 1 for process creation, Sysmon Event ID 11 for file creation, PowerShell Script Block Logging events, Microsoft Defender for Endpoint advanced hunting tables, EDR process/file telemetry, and vulnerability management patch state. Absence of these artifacts does not prove non-exploitation, because information disclosure may leave minimal forensic traces unless the attacker performs follow-on activity.

What your security team should do

• Deploy the applicable Microsoft cumulative security update to affected Windows desktop and server versions during the next standard patch cycle, or sooner for systems used by many users or handling sensitive data.
• Use endpoint vulnerability management to identify Windows 10, Windows 11, Windows Server 2022, and Windows Server 2025 systems missing the relevant security update.
• Prioritize shared workstations, jump hosts, administrative workstations, terminal servers, and servers where low-privileged local access is available to multiple users.
• Maintain least-privilege controls and restrict interactive logon rights on servers to reduce the number of users who could exploit local information disclosure flaws.
• Hunt for unusual local reconnaissance, suspicious Windows Shell child processes, credential discovery behavior, and unexpected access to sensitive user or system locations, recognizing that there are no public exploit-specific indicators in the supplied data.
• Continue monitoring vendor guidance and threat intelligence feeds; current EPSS is low, exploit maturity is listed as none, and the vulnerability is not in CISA KEV, but this may change if exploit details become public.