Microsoft Windows up to Server 2019 Remote Desktop Service DejaBlue access control

Summaryinfo

A vulnerability was found in Microsoft Windows up to Server 2019. It has been classified as critical. This impacts an unknown function of the component Remote Desktop Service. The manipulation leads to access control (DejaBlue). This vulnerability is uniquely identified as CVE-2019-1226. The attack is possible to be carried out remotely. No exploit exists. To fix this issue, it is recommended to deploy a patch.

Detailsinfo

A vulnerability, which was classified as critical, has been found in Microsoft Windows up to Server 2019 (Operating System). This issue affects an unknown code block of the component Remote Desktop Service. The manipulation with an unknown input leads to a access control vulnerability (DejaBlue). Using CWE to declare the problem leads to CWE-284. The product does not restrict or incorrectly restricts access to a resource from an unauthorized actor. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

A remote code execution vulnerability exists in Remote Desktop Services – formerly known as Terminal Services – when an unauthenticated attacker connects to the target system using RDP and sends specially crafted requests. This vulnerability is pre-authentication and requires no user interaction. An attacker who successfully exploited this vulnerability could execute arbitrary code on the target system. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights. To exploit this vulnerability, an attacker would need to send a specially crafted request to the target systems Remote Desktop Service via RDP. The update addresses the vulnerability by correcting how Remote Desktop Services handles connection requests.

The weakness was disclosed 08/13/2019 as confirmed security update guide (Website). It is possible to read the advisory at portal.msrc.microsoft.com. The public release has been coordinated in cooperation with Microsoft. The identification of this vulnerability is CVE-2019-1226. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. The technical details are unknown and an exploit is not publicly available. The pricing for an exploit might be around USD $5k-$25k at the moment (estimation calculated on 02/21/2026). The attack technique deployed by this issue is T1068 according to MITRE ATT&CK. The advisory points out:

A remote code execution vulnerability exists in Remote Desktop Services – formerly known as Terminal Services – when an unauthenticated attacker connects to the target system using RDP and sends specially crafted requests. This vulnerability is pre-authentication and requires no user interaction. An attacker who successfully exploited this vulnerability could execute arbitrary code on the target system. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights.

Applying a patch is able to eliminate this problem. A possible mitigation has been published immediately after the disclosure of the vulnerability.

The entries VDB-139911, VDB-139909, VDB-139908 and VDB-139910 are pretty similar. Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Productinfo

Type

• Operating System

Vendor

• Microsoft

Name

• Windows

Version

• 10 1803
• 10 1809
• 10 1903
• Server 1803
• Server 1903
• Server 2019

License

• commercial

Website

• Vendor: https://www.microsoft.com/
• Product: https://www.microsoft.com/en-us/windows

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