Critical bugs in CredSSP allow remote code execution on Servers
Category : Blog
CredSSP allow remote code
The newly discovered Credential Security Support Provider protocol (CredSSP) vulnerability on the Windows platform allows hackers to use Remote Desktop Protocol (RDP) and Windows Remote Manager (WinRM) to remotely steal data or run malicious code. The CredSSP protocol was originally designed to provide cryptographic authentication when Windows hosts use RDP or WinRM for remote connections.
This vulnerability (CVE-2018-0886) was discovered by a researcher at a company named Preempt Security. There is a logical encryption vulnerability in the CredSSP protocol. A hacker can use a wireless connection to initiate a man-in-the-middle attack. Physical connection to the network, you can also initiate a remote call (Remote Procedure Call) to steal the authentication information in the computer process.
How Does CredSSP Attack Work?
An attacker can exploit this vulnerability in conjunction with a man-in-the-middle attack. The attacker will set up the man-in-the-middle, wait for a CredSSP session to occur, and once it does, will steal session authentication and perform a Remote Procedure Call (DCE/RPC) attack on the server that the user originally connected to (e.g., the server user connected with RDP). An attacker which have stolen a session from a user with sufficient privileges could run different commands with local admin privileges. This is especially critical in case of domain controllers, where most Remote Procedure Calls (DCE/RPC) are enabled by default.
CredSSP attack could be mounted list:
An attacker with WiFi/Physical access – If an attacker has some physical access to your network, then he could easily launch a man-in-the-middle attack. If you also have WiFi deployed in areas of your network, you might be vulnerable to key reinstallation attacks (KRACK), thus making all machines that do RDP via WiFI exposed to this new attack.
Address Resolution Protocol (ARP) poisoning – Despite being an old attack technique, many networks are still not 100% protected from ARP poisoning. If this is the case in your network, this new vulnerability means an attacker with control of one machine could easily move laterally and infect all machines in the same network segment.
Attacking sensitive servers (including domain controllers) – Sometimes, an attacker has control of several workstations in an organization and needs to find a way to infect sensitive business-critical servers (which might require higher privileges).
Most corporate internal networks use the Windows RDP protocol for remote login. Preempt’s researchers reported this vulnerability to Microsoft last August but until now Microsoft released a patch for the vulnerability.
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