Speculative Store Bypass (SSB) () is the name given to a hardware security vulnerability and its exploitation that takes advantage of
speculative execution
Speculative execution is an optimization (computer science), optimization technique where a computer system performs some task that may not be needed. Work is done before it is known whether it is actually needed, so as to prevent a delay that woul ...
in a similar way to the
Meltdown and
Spectre
Spectre, specter or the spectre may refer to:
Religion and spirituality
* Vision (spirituality)
* Apparitional experience
* Ghost
Arts and entertainment Film and television
* ''Spectre'' (1977 film), a made-for-television film produced and writt ...
security vulnerabilities.
It affects the
ARM
In human anatomy, the arm refers to the upper limb in common usage, although academically the term specifically means the upper arm between the glenohumeral joint (shoulder joint) and the elbow joint. The distal part of the upper limb between ...
,
AMD
Advanced Micro Devices, Inc. (AMD) is an American multinational corporation and technology company headquartered in Santa Clara, California and maintains significant operations in Austin, Texas. AMD is a hardware and fabless company that de ...
and
Intel
Intel Corporation is an American multinational corporation and technology company headquartered in Santa Clara, California, and Delaware General Corporation Law, incorporated in Delaware. Intel designs, manufactures, and sells computer compo ...
families of processors. It was discovered by researchers at
Microsoft Security Response Center and
Google Project Zero (GPZ).
After being leaked on 3 May 2018 as part of a group of eight additional Spectre-class flaws provisionally named ''
Spectre-NG'',
it was first disclosed to the public as "Variant 4" on 21 May 2018, alongside a related speculative execution vulnerability designated "
Variant 3a".
Details
Speculative execution exploit Variant 4,
is referred to as Speculative Store Bypass (SSB),
and has been assigned .
SSB is named Variant 4, but it is the fifth variant in the Spectre-Meltdown class of vulnerabilities.
Steps involved in exploit:
# "Slowly" store a value at a memory location
# "Quickly" load that value from that memory location
# Utilize the value that was just read to disrupt the cache in a detectable way
Impact and mitigation
Intel claims that web browsers that are already patched to mitigate Spectre Variants 1 and 2 are partially protected against Variant 4.
Intel said in a statement that the likelihood of end users being affected was "low" and that not all protections would be on by default due to some impact on performance.
The Chrome JavaScript team confirmed that effective mitigation of Variant 4 in software is infeasible, in part due to performance impact.
Intel is planning to address Variant 4 by releasing a
microcode
In processor design, microcode serves as an intermediary layer situated between the central processing unit (CPU) hardware and the programmer-visible instruction set architecture of a computer. It consists of a set of hardware-level instructions ...
patch that creates a new hardware flag named ''
Speculative Store Bypass Disable (SSBD)''.
A
stable
A stable is a building in which working animals are kept, especially horses or oxen. The building is usually divided into stalls, and may include storage for equipment and feed.
Styles
There are many different types of stables in use tod ...
microcode patch is yet to be delivered, with Intel suggesting that the patch will be ready "in the coming weeks".
Many operating system vendors will be releasing software updates to assist with mitigating Variant 4;
however, microcode/
firmware
In computing
Computing is any goal-oriented activity requiring, benefiting from, or creating computer, computing machinery. It includes the study and experimentation of algorithmic processes, and the development of both computer hardware, h ...
updates are required for the software updates to have an effect.
Speculative execution exploit variants
References
See also
*
Speculative execution CPU vulnerabilities
Transient execution CPU vulnerabilities are vulnerabilities in which instructions, most often optimized using speculative execution, are executed temporarily by a microprocessor, without committing their results due to a misprediction or error, re ...
External links
Website detailing the Meltdown and Spectre vulnerabilities, hosted by Graz University of Technology Gibson Research Corporation
{{Hacking in the 2010s
Transient execution CPU vulnerabilities
2018 in computing
X86 memory management