Dark Reading is part of the Informa Tech Division of Informa PLC

This site is operated by a business or businesses owned by Informa PLC and all copyright resides with them.Informa PLC's registered office is 5 Howick Place, London SW1P 1WG. Registered in England and Wales. Number 8860726.

Vulnerabilities / Threats

New Vulnerabilities Make RDP Risks Far from Remote

More than two dozen vulnerabilities raise the risk of using RDP clients to remotely manage and configure systems.

Researchers have announced a flurry of vulnerabilities in three separate implementations of RDP, the remote desktop protocol that is widely used in remote technical support and configuration operations at large enterprises and service providers.

In a presentation at their company's annual conference, Check Point security researchers detailed 25 "reverse RDP" vulnerabilities in three separate RDP clients: FreeRDP, rdesktop, and mstc.exe. Two of the clients are native to operating systems; rdesktop is the client included in distros of Kali Linux, while mstc.exe is Microsoft's RDP client included with Windows.

In all of these reverse RDP vulnerabilities, it's the remote system — not the system being connected to — that's vulnerable. As Yaniv Balmas, head of technical research at Check Point, says, "Once we have a direct channel back to your to your machine, we can practically do anything we want on that machine. We can do everything we want. The machine is ours."

While many IT professionals believe that only display and user interface data is exchanged in an RDP session, Balmas says RDP clients have more capabilities, and it's those additional capabilities that provide the source of the vulnerabilities.

In both of the open source RDP clients, Check Point found that malware on the "host" system could use a buffer overflow technique to force remote code execution on the client machine. There are actually a variety of ways to do this; so far, 19 vulnerabilities have been identified and given CVE designations in rdesktop, while six have been identified in FreeRDP.

All of these vulnerabilities were submitted to the open source community prior to public disclosure, and all have been patched. "So the remediation for the two free versions is essentially to make sure you're using the latest patched version," Balmas says.

The situation with mstc.exe is different. The researchers found that the code Microsoft uses is much stronger than that used by the open source versions. There's one feature, though, that creates an opportunity for malicious behavior: Through the RDP client, the host and remote systems share a clipboard.

As the researcher wrote in their blog post on the vulnerabilities, "If the client fails to properly canonicalize and sanitize the file paths it receives, it could be vulnerable to a path-traversal attack, allowing the server to drop arbitrary files in arbitrary paths on the client’s computer, a very strong attack primitive."

What this means in practical terms also is detailed in the post: "If a client uses the 'Copy & Paste' feature over an RDP connection, a malicious RDP server can transparently drop arbitrary files to arbitrary file locations on the client’s computer, limited only by the permissions of the client. For example, we can drop malicious scripts to the client’s 'Startup' folder, and after a reboot they will be executed on his computer, giving us full control."

The researchers were able to build code that pushed code onto the clipboard without the user's permission or awareness, Balmas says. Then, if the remote user pastes anything from the clipboard, the malicious code is also pasted to an arbitrary location.

Because the exploit involves user interaction, Microsoft does not classify this as a code vulnerability and has not been given a CVE designation. Despite that, "We consider this to be critical, or at least important for users to know, because we think that this kind of — I would call it the bug — goes unnoticed and can definitely be used by malicious actors," Balmas says.

Related Content:

Curtis Franklin Jr. is Senior Editor at Dark Reading. In this role he focuses on product and technology coverage for the publication. In addition he works on audio and video programming for Dark Reading and contributes to activities at Interop ITX, Black Hat, INsecurity, and ... View Full Bio

Comment  | 
Print  | 
More Insights
Comments
Newest First  |  Oldest First  |  Threaded View
kscherler
100%
0%
kscherler,
User Rank: Apprentice
2/18/2019 | 5:31:33 PM
MSTC? Isn't it MSTSC?
As a guy who has to type mstsc about 100 times a day I would ask that you please fix your spelling of the microsoft terminal services client when referencing it. You used mstc several times in your article instead of mstsc.
Engr.Zaheer
50%
50%
Engr.Zaheer,
User Rank: Apprentice
2/6/2019 | 10:20:20 AM
New Vulnerabilities Make RDP Risks Far From Remote
Will this be the issue if your are using RDP within a LAN/private environment. Its risk will be restricted to only that environment ?
10 Ways to Keep a Rogue RasPi From Wrecking Your Network
Curtis Franklin Jr., Senior Editor at Dark Reading,  7/10/2019
The Security of Cloud Applications
Hillel Solow, CTO and Co-founder, Protego,  7/11/2019
Where Businesses Waste Endpoint Security Budgets
Kelly Sheridan, Staff Editor, Dark Reading,  7/15/2019
Register for Dark Reading Newsletters
White Papers
Video
Cartoon Contest
Write a Caption, Win a Starbucks Card! Click Here
Latest Comment: "Jim, stop pretending you're drowning in tickets."
Current Issue
Building and Managing an IT Security Operations Program
As cyber threats grow, many organizations are building security operations centers (SOCs) to improve their defenses. In this Tech Digest you will learn tips on how to get the most out of a SOC in your organization - and what to do if you can't afford to build one.
Flash Poll
The State of IT Operations and Cybersecurity Operations
The State of IT Operations and Cybersecurity Operations
Your enterprise's cyber risk may depend upon the relationship between the IT team and the security team. Heres some insight on what's working and what isn't in the data center.
Twitter Feed
Dark Reading - Bug Report
Bug Report
Enterprise Vulnerabilities
From DHS/US-CERT's National Vulnerability Database
CVE-2019-13360
PUBLISHED: 2019-07-16
In CentOS-WebPanel.com (aka CWP) CentOS Web Panel 0.9.8.836, remote attackers can bypass authentication in the login process by leveraging knowledge of a valid username.
CVE-2019-13383
PUBLISHED: 2019-07-16
In CentOS-WebPanel.com (aka CWP) CentOS Web Panel 0.9.8.846, the Login process allows attackers to check whether a username is valid by reading the HTTP response.
CVE-2019-13603
PUBLISHED: 2019-07-16
An issue was discovered in the HID Global DigitalPersona (formerly Crossmatch) U.are.U 4500 Fingerprint Reader Windows Biometric Framework driver 5.0.0.5. It has a statically coded initialization vector to encrypt a user's fingerprint image, resulting in weak encryption of that. This, in combination...
CVE-2019-13605
PUBLISHED: 2019-07-16
In CentOS-WebPanel.com (aka CWP) CentOS Web Panel 0.9.8.838 to 0.9.8.846, remote attackers can bypass authentication in the login process by leveraging the knowledge of a valid username. The attacker must defeat an encoding that is not equivalent to base64, and thus this is different from CVE-2019-1...
CVE-2019-13615
PUBLISHED: 2019-07-16
VideoLAN VLC media player 3.0.7.1 has a heap-based buffer over-read in mkv::demux_sys_t::FreeUnused() in modules/demux/mkv/demux.cpp when called from mkv::Open in modules/demux/mkv/mkv.cpp.