Jason Geffner, a security researcher at Crowdstrike, has released information about a new, unchecked buffer vulnerability called VENOM affecting the open source QEMU virtualization platform which provides virtualization capabilities similar to VMWare or Microsoft’s Hyper-V.
The initial reports indicate this is a serious vulnerability, and while the vulnerability itself is serious, the overall scope is limited. People should treat this as a serious situation, but not view it as a broad crisis like “Heartbleed,” for instance.
The Vulnerability
The unchecked buffer vulnerability (CVE-2015-3456) occurs in the code for QEMU’s virtual floppy disk controller. A successful buffer overflow attack exploiting this vulnerability can enable an attacker to execute his or her code in the hypervisor’s security context and escape from the guest operating system to gain control over the entire host.
Because QEMU is an open source package it’s nearly impossible to know all affected products or services. However, Crowdstrike has indicated that it does affect Xen, KVM and the native QEMU client.
We do know that neither VMWare’s nor Microsoft’s virtualization products are vulnerable. Amazon has also stated that their AWS platform is not affected.
QEMU and XEN already have patches available. Other vendors are presumably working on patches, as well.
The Risks
In terms of the vulnerability itself, a determined attacker could potentially compromise all virtual instances on the host. A compromised host could also be used to stage lateral movement attacks against the hosting environment, putting other hosts and virtual instances at risk. To do this, an attacker would need to have a virtual machine on a vulnerable host and be able to load and execute code of their choosing onto the host. The attacker would also need administrator privileges on the guest OS. At that point, the attacker could have control of the host and potentially leverage that compromised host to launch other attacks on the network.
For environments that have the vulnerable code on their systems, this is a very serious vulnerability that should be addressed as quickly as possible. Similar to other open source vulnerabilities, like Heartbleed and Shellshock, obtaining and deploying patches will be a challenge due to the fractured nature of the ecosystem. Administrators should be prepared for these difficulties and plan for contingencies to mitigate those risks.
The Ramifications
While this isn’t a vulnerability that would appear to affect the industry as broadly as some others, it is virtual machine escape vulnerability in the default configuration: this is the worst type of vulnerability for virtual machine environments. Even if you’re not directly affected by this vulnerability, if you run virtual machines in your environment, you should use this new vulnerability as an indication it is time to plan your response and mitigations for the day when a vulnerability just like this will affect your environment.
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