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ADVISORY: Intel…Simply Misunderstood?

by Steve Tilson on May 11, 2018

To close numerous security gaps, Microsoft, Adobe, Apple, Red Hat, Xen, VMware and other vendors have released a number of patches in the first 10 days of May. We discussed some of these in our recent blog post, Microsoft May Madness. However, one issue that stands out because it impacts multiple operating system platforms is the chip giant Intel’s CVE-2018-8897. A problem that’s being framed as a “developers documentation misunderstanding” has turned into a cross-platform patch requirement to secure the kernel. To be clear, the issue doesn’t exist in the chip itself – rather, in the way developers have built their software stacks to interact with the processor.

Modern processors provide a hardware debugging infrastructure that allows system designers and developers to debug their system and monitor events. When such events occur during the course of program execution, a debug exception is raised. Developers at various vendors misunderstood Intel’s documentation about the way processors handle that exception. This has led to a flaw being present on multiple platforms that could allow unauthenticated users to read sensitive data in memory or control low-level operating system functions by gaining elevated privileges. The flaw was reported by researchers Nick Peterson of Everdox Tech and Nemanja Mulasmajic of triplefault.io in their detailed white paper POP SS/MOV SS Vulnerability.

Analysis

The vulnerability itself is not remotely exploitable and an attacker would need to have access to the system. At the time of publication, there’s no indication that attackers have exploited the issue on any operating system. Also, no proof of concept exploit code has been publicly released. However, it should be noted that some researchers have stated that they can exploit Windows systems and should be able to exploit Linux as well. Hence, our recommendation is to mitigate as soon as possible.

Solution

Refer to vendor-specific documentation for patching.

Intel has released the following statement, according to Digitpol: “The security of our customers and partners is important to us. To help ensure clear communication with the developer community, we are updating our Software Developers Manual (SDM) with clarifying language on the secure use of the POP/MOV-SS instructions. We recommend that system software vendors evaluate their software to confirm their products handle the situations in question.”