Microsoft Remote Desktop Services (RDP8) license negotiation denial-of-service vulnerability [CVE-2019-1453]

CVE number – CVE-2019-1453

An exploitable denial-of-service vulnerability exists in the RDP8 implementation of Microsoft’s Remote Desktop Services. A certain component of license negotiation can allow a remote client to read an amount of memory that is controlled by the client.

Due to this, a client can coerce the component to read from memory that is unmapped, resulting in a denial-of-service condition. An attacker can negotiate capabilities and then send a particular packet type in order to trigger this vulnerability.

This denial-of-service vulnerability exist only on RDP8. RDP7, which is implemented in kernel-space, does not use the channels described within this document, and therefore is not vulnerable.

Remote Desktop Services allow a user or administrator to take control of a remote computer over a network connection. This allows the user to utilize a familiar graphical user interface to interact with said remote machine which provides a thin-client architecture on the Windows platform.

These capabilities are accomplished using the Remote Desktop Protocol which is built on top of the X.224, T.124, T.125, T.128 protocols. Remote Desktop Services is a common service within the enterprise and is commonly used as a work-around on a network with otherwise minimalistic remote administration capabilities.

Discovered by a member of Cisco Talos.

Jason Davies

UK based technology professional, with an interest in computer security and telecoms.

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