<s>
Speculative	B-Error_Name
Store	I-Error_Name
Bypass	I-Error_Name
(	O
SSB	B-Error_Name
)	O
(	O
)	O
is	O
the	O
name	O
given	O
to	O
a	O
hardware	O
security	O
vulnerability	O
and	O
its	O
exploitation	O
that	O
takes	O
advantage	O
of	O
speculative	B-General_Concept
execution	I-General_Concept
in	O
a	O
similar	O
way	O
to	O
the	O
Meltdown	B-Architecture
and	O
Spectre	B-Error_Name
security	O
vulnerabilities	O
.	O
</s>
<s>
It	O
affects	O
the	O
ARM	B-Architecture
,	O
AMD	O
and	O
Intel	O
families	O
of	O
processors	O
.	O
</s>
<s>
After	O
being	O
leaked	O
on	O
3	O
May	O
2018	O
as	O
part	O
of	O
a	O
group	O
of	O
eight	O
additional	O
Spectre-class	B-Error_Name
flaws	I-Error_Name
provisionally	O
named	O
Spectre-NG	O
,	O
it	O
was	O
first	O
disclosed	O
to	O
the	O
public	O
as	O
"	O
Variant	B-Error_Name
4	I-Error_Name
"	O
on	O
21	O
May	O
2018	O
,	O
alongside	O
a	O
related	O
speculative	B-General_Concept
execution	I-General_Concept
vulnerability	O
designated	O
"	O
Variant	O
3a	O
"	O
.	O
</s>
<s>
Speculative	B-General_Concept
execution	I-General_Concept
exploit	O
Variant	B-Error_Name
4	I-Error_Name
,	O
is	O
referred	O
to	O
as	O
Speculative	B-Error_Name
Store	I-Error_Name
Bypass	I-Error_Name
(	O
SSB	B-Error_Name
)	O
,	O
and	O
has	O
been	O
assigned	O
.	O
</s>
<s>
SSB	B-Error_Name
is	O
named	O
Variant	B-Error_Name
4	I-Error_Name
,	O
but	O
it	O
is	O
the	O
fifth	O
variant	O
in	O
the	O
Spectre-Meltdown	O
class	O
of	O
vulnerabilities	O
.	O
</s>
<s>
Intel	O
claims	O
that	O
web	O
browsers	O
that	O
are	O
already	O
patched	O
to	O
mitigate	O
Spectre	B-Error_Name
Variants	O
1	O
and	O
2	O
are	O
partially	O
protected	O
against	O
Variant	B-Error_Name
4	I-Error_Name
.	O
</s>
<s>
The	O
Chrome	O
JavaScript	O
team	O
confirmed	O
that	O
effective	O
mitigation	O
of	O
Variant	B-Error_Name
4	I-Error_Name
in	O
software	O
is	O
infeasible	O
,	O
in	O
part	O
due	O
to	O
performance	O
impact	O
.	O
</s>
<s>
Intel	O
is	O
planning	O
to	O
address	O
Variant	B-Error_Name
4	I-Error_Name
by	O
releasing	O
a	O
microcode	B-Device
patch	O
that	O
creates	O
a	O
new	O
hardware	O
flag	O
named	O
Speculative	B-Error_Name
Store	I-Error_Name
Bypass	I-Error_Name
Disable	O
(	O
SSBD	O
)	O
.	O
</s>
<s>
A	O
stable	O
microcode	B-Device
patch	O
is	O
yet	O
to	O
be	O
delivered	O
,	O
with	O
Intel	O
suggesting	O
that	O
the	O
patch	O
will	O
be	O
ready	O
"	O
in	O
the	O
coming	O
weeks	O
"	O
.	O
</s>
<s>
Many	O
operating	O
system	O
vendors	O
will	O
be	O
releasing	O
software	O
updates	O
to	O
assist	O
with	O
mitigating	O
Variant	B-Error_Name
4	I-Error_Name
;	O
however	O
,	O
microcode/firmware	O
updates	O
are	O
required	O
for	O
the	O
software	O
updates	O
to	O
have	O
an	O
effect	O
.	O
</s>
