VENOM Vulnerability Disclosure
VENOM Vulnerability Disclosure – CVE-2015-3456
A new vulnerability called VENOM, Virtualized Environment Neglected Operations Manipulation, has been discovered (CVE-2015-3456).
What is the vulnerability (per Crowdstrike)?
“The guest operating system communicates with the FDC by sending commands such as seek, read, write, format, etc. to the FDC’s input/output port. QEMU’s virtual FDC uses a fixed-size buffer for storing these commands and their associated data parameters. The FDC keeps track of how much data to expect for each command and, after all expected data for a given command is received from the guest system, the FDC executes the command and clears the buffer for the next command. This buffer reset is performed immediately at the completion of processing for all FDC commands, except for two of the defined commands. An attacker can send these commands and specially crafted parameter data from the guest system to the FDC to overflow the data buffer and execute arbitrary code in the context of the host’s hypervisor process.”
The reach and risk level of this vulnerability can be visualized in the relationship between the hypervisor (host) and the guest (virtual machine). It is possible, through this type of vulnerability, to bypass the protection rings of the virtualization architecture.
Basically, this vulnerability would allow an attacker craft malicious code against two specific commands used to communicate with the floppy disc controller (FDC) of the VM where a buffer reset is not performed thereby allowing overflow of the data buffer and execute code on the host, effectively escaping hypervisor (host) limitations. This also opens the possibility of pivoting or lateral movement against peers or co-tenants in cloud environments (PAAS, IAAS).
Xen, KVM, Oracle VM VirtualBox and the native QEMU client.
VMware, Microsoft Hyper-V, and Bochs hypervisors
No proof of concept is available yet. The researcher claims the vulnerability is agnostic as it can affect the virtualization platform and guest regardless of what operating system is in question such as Linux, Windows, Mac OS. Although this agnosticity increases the reach and risk of this vulnerability it may limit it as well when it comes to escalating and moving through virtual environments, likely requiring additional items in the exploitation chain that allow privilege escalation or multi stage exploitation in order to successfully pivot, and move laterally in virtualization environments. However, the successful exploitation of this vulnerability still gives the attacker the possibility of command execution in the host, some of which are mentioned in the vulnerability description, such as seek, read, write, format.
The following are a number of sites that provide patch information. Further research and customization is suggested.
The following items are suggested to mitigate this vulnerability, if applicable. These items are provided as guidance and are not to be taken as extensive. Further research and adaptation of these times are needed, depending on every different environment.