There's a new speculative execution side-channel vulnerability akin to Spectre and Meltdown, but this one is different in a crucial way: it's aimed at program data rather than program instructions.
The new vulnerability, described in CERT Vulnerability Note VU#982149, is similar to Spectre in that it leverages speculative execution — a process by which certain computer instructions are executed in case they're the next instructions called for by the software. This is a technique that speeds up code execution on just about all modern CPUs.
It differs from Spectre in that it's not working on the part of memory-holding instructions. Instead, the new vulnerability - called Foreshadow, or L1TF - targets the L1 data cache.
"Researchers simply followed the thread left by Spectre and Meltdown — this isn't a completely new class of vulnerabilities," says Matthew Chiodi, vice president of cloud security at RedLock.
Intel yesterday released a pair of security notifications on the vulnerability. The first focuses on the hardware details, and discusses the implications for operating system and VM developers. According to Intel, microcode has been developed and pushed live to help mitigate the effects of the vulnerability.
In its Intel Software Developer blog, Intel explores the impact on application developers and provides possible mitigations for programmers working on browsers, applications in VMs, etc.
Google Cloud Security published a blog post on the vulnerability, noting that, "Directly exploiting these vulnerabilities requires control of hardware resources that are accessible only with operating system level control of the underlying physical or virtual processors."
That's similar to other Spectre-like vulnerabilities and one of the key reasons most security professionals seem more curious than panic-stricken about this class of vulnerabilities.
Google also noted that the primary danger of Foreshadow is that a threat actor could use it to reach across virtual machine boundaries, gaining access to the information belonging to another virtual machine — and possibly, another organization.
"Systems that utilize software-defined storage via a mid-layer filesystem will likely experience the most impact. Many software-defined storage solutions, which use a mid-layer filesystem will likely have a much larger performance impact as a result of these fixes," says Jeff Ready, CEO of Scale Computing.
Ken Spinner, vice president of field engineering at Varonis, says this attack can glean sensitive data from the target. "The prize of an attack like this is sensitive data. If passwords or other credentials can be directly extracted and then exploited, it's obviously a win for attackers," he says.
The benefits of virtual machines in the cloud are based on the ability to maintain clear, clean boundaries between virtual servers, he says. "This entire class of processor attacks proves how hard that can be in practice. Securing virtual services can directly increase operational costs for cloud providers, leading to gaps in some cases," he says.
Few security professionals are panicked about this class of speculative-execution vulnerabilities due to the difficulty and complexity in developing the attacks, getting them implanted on a target machine, and sorting through slowly growing piles of data in the hopes of finding something interesting. "Why slip in through the second story window when the front door is unlocked?" Spinner says.
Nonetheless, Foreshadow is seen by most observers as yet another call to make sure an organization's update and patch policies are strong and ready for waves of remediating updates.
"How far this goes and how much damage it does depends greatly on whether people install the patch," says Michael Daly, CTO for Raytheon's cybersecurity and special missions. "Unfortunately, history tells us many will not. While this particular threat seems minor for now, since so few systems use SGX, that can change."
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