Security Bypass Issue Found in Windows Remote Assistance

Microsoft has addressed a security weakness in Windows Remote Assistance that could allow attackers to bypass built-in protection mechanisms and access sensitive data under certain conditions. The vulnerability, tracked as CVE-2026-20824, has been rated Important and mainly impacts how Windows applies trust checks to files involved in Remote Assistance sessions.

While the issue does not enable full system takeover, it weakens safeguards designed to protect users from untrusted content, making it particularly relevant in post-compromise or insider attack scenarios.

How the Vulnerability Works

The flaw lies in how Windows Remote Assistance handles specially crafted files used to start or manage assistance sessions. In some cases, these files are processed in a way that skips normal security checks, allowing them to appear more trusted than they actually are.

As a result, protections tied to Mark of the Web (MOTW)—such as warning prompts, SmartScreen checks, and certain script or macro restrictions—may not be enforced.

This means content that originated from the internet could be opened locally without the usual defenses, increasing the risk of stealthy data access or follow-on attacks.

Exploitation requires user interaction, typically by convincing a victim to open a malicious file delivered through email, messaging platforms, or a web download.

Impact, Affected Systems, and Mitigation

Impact: Enables attackers to bypass Mark of the Web protections, potentially allowing sensitive data access or stealthy follow-on attacks without triggering expected security warnings.
Affected Systems: Supported versions of Windows 10, Windows 11, and Windows Server, including both client and enterprise deployments.
Mitigation: Microsoft has addressed the issue in the January 2026 Patch Tuesday updates. Organizations should apply the updates as soon as possible. Until patching is complete, administrators are advised to restrict Windows Remote Assistance usage, enhance email and web filtering controls, and remind users to avoid opening unsolicited assistance files or attachments.

Applying the latest security updates restores proper protection checks and significantly reduces the risk of this bypass technique being exploited.