<s>
Stagefright	B-Application
is	O
the	O
name	O
given	O
to	O
a	O
group	O
of	O
software	B-Error_Name
bugs	I-Error_Name
that	O
affect	O
versions	O
from	O
2.2	B-Application
"	I-Application
Froyo	I-Application
"	I-Application
up	O
until	O
5.1.1	B-Application
"	I-Application
Lollipop	I-Application
"	I-Application
of	O
the	O
Android	B-Application
operating	I-Application
system	I-Application
exposing	O
an	O
estimated	O
950	O
million	O
devices	O
(	O
95%	O
of	O
all	O
Android	B-Application
devices	O
)	O
at	O
the	O
time	O
.	O
</s>
<s>
Exploitation	O
of	O
the	O
bug	B-Error_Name
allows	O
an	O
attacker	O
to	O
perform	O
arbitrary	O
operations	O
on	O
the	O
victim	O
's	O
device	O
through	O
remote	O
code	O
execution	O
and	O
privilege	O
escalation	O
.	O
</s>
<s>
Security	O
researchers	O
demonstrate	O
the	O
bugs	B-Error_Name
with	O
a	O
proof	O
of	O
concept	O
that	O
sends	O
specially	O
crafted	O
MMS	O
messages	O
to	O
the	O
victim	O
device	O
and	O
in	O
most	O
cases	O
requires	O
no	O
end-user	O
actions	O
upon	O
message	O
reception	O
to	O
succeed	O
—	O
the	O
user	O
does	O
n't	O
have	O
to	O
do	O
anything	O
to	O
'	O
accept	O
 '	O
exploits	O
using	O
the	O
bug	B-Error_Name
;	O
it	O
happens	O
in	O
the	O
background	O
.	O
</s>
<s>
The	O
underlying	O
attack	O
vector	O
exploits	O
certain	O
integer	B-Error_Name
overflow	I-Error_Name
vulnerabilities	O
in	O
the	O
Android	B-Application
core	O
component	O
called	O
,	O
which	O
is	O
a	O
complex	O
software	B-Library
library	I-Library
implemented	O
primarily	O
in	O
C++	B-Language
as	O
part	O
of	O
the	O
Android	B-Application
Open	B-License
Source	I-License
Project	O
(	O
AOSP	O
)	O
and	O
used	O
as	O
a	O
backend	O
engine	O
for	O
playing	O
various	O
multimedia	O
formats	O
such	O
as	O
MP4	O
files	O
.	O
</s>
<s>
The	O
discovered	O
bugs	B-Error_Name
have	O
been	O
provided	O
with	O
multiple	O
Common	O
Vulnerabilities	O
and	O
Exposures	O
(	O
CVE	O
)	O
identifiers	O
,	O
(	O
the	O
latter	O
one	O
has	O
been	O
assigned	O
separately	O
from	O
the	O
others	O
)	O
,	O
which	O
are	O
collectively	O
referred	O
to	O
as	O
the	O
Stagefright	B-Application
bug	B-Error_Name
.	O
</s>
<s>
The	O
Stagefright	B-Application
bug	B-Error_Name
was	O
discovered	O
by	O
Joshua	O
Drake	O
from	O
the	O
Zimperium	O
security	O
firm	O
,	O
and	O
was	O
publicly	O
announced	O
for	O
the	O
first	O
time	O
on	O
July	O
27	O
,	O
2015	O
.	O
</s>
<s>
Prior	O
to	O
the	O
announcement	O
,	O
Drake	O
reported	O
the	O
bug	B-Error_Name
to	O
Google	B-Application
in	O
April	O
2015	O
,	O
which	O
incorporated	O
a	O
related	O
bugfix	O
into	O
its	O
internal	O
source	B-General_Concept
code	I-General_Concept
repositories	I-General_Concept
two	O
days	O
after	O
the	O
report	O
.	O
</s>
<s>
In	O
July	O
2015	O
,	O
Evgeny	O
Legerov	O
,	O
a	O
Moscow-based	O
security	O
researcher	O
,	O
announced	O
that	O
he	O
had	O
found	O
at	O
least	O
two	O
similar	O
heap	B-General_Concept
overflow	I-General_Concept
zero-day	O
vulnerabilities	O
in	O
the	O
Stagefright	B-Application
library	O
,	O
claiming	O
at	O
the	O
same	O
time	O
that	O
the	O
library	O
has	O
been	O
already	O
exploited	O
for	O
a	O
while	O
.	O
</s>
<s>
Legerov	O
also	O
confirmed	O
that	O
the	O
vulnerabilities	O
he	O
discovered	O
become	O
unexploitable	O
by	O
applying	O
the	O
patches	O
Drake	O
submitted	O
to	O
Google	B-Application
.	I-Application
</s>
<s>
The	O
public	O
full	O
disclosure	O
of	O
the	O
Stagefright	B-Application
bug	B-Error_Name
,	O
presented	O
by	O
Drake	O
,	O
took	O
place	O
on	O
August	O
5	O
,	O
2015	O
at	O
the	O
Black	O
Hat	O
USA	O
computer	O
security	O
conference	O
,	O
and	O
on	O
August	O
7	O
,	O
2015	O
at	O
the	O
DEF	O
CON23	O
hacker	O
convention	O
.	O
</s>
<s>
Following	O
the	O
disclosure	O
,	O
on	O
August	O
5	O
,	O
2015	O
,	O
Zimperium	O
publicly	O
released	O
the	O
source	O
code	O
of	O
a	O
proof-of-concept	O
exploit	O
,	O
actual	O
patches	O
for	O
the	O
Stagefright	B-Application
library	O
(	O
although	O
the	O
patches	O
were	O
already	O
publicly	O
available	O
since	O
early	O
May	O
2015	O
in	O
the	O
AOSP	O
and	O
other	O
open-source	B-License
repositories	B-General_Concept
)	O
,	O
and	O
an	O
Android	B-Application
application	I-Application
called	O
"	O
Stagefright	B-Application
detector	O
"	O
that	O
tests	O
whether	O
an	O
Android	B-Application
device	O
is	O
vulnerable	O
to	O
the	O
Stagefright	B-Application
bug	B-Error_Name
.	O
</s>
<s>
On	O
August	O
13	O
,	O
2015	O
,	O
another	O
Stagefright	B-Application
vulnerability	O
,	O
,	O
was	O
published	O
by	O
Exodus	O
Intelligence	O
.	O
</s>
<s>
CyanogenMod	O
team	O
published	O
a	O
notice	O
that	O
patches	O
for	O
CVE-2015-3864	B-Application
have	O
been	O
incorporated	O
in	O
CyanogenMod	O
12.1	O
source	O
on	O
August	O
13	O
,	O
2015	O
.	O
</s>
<s>
On	O
October	O
1	O
,	O
2015	O
,	O
Zimperium	O
released	O
details	O
of	O
further	O
vulnerabilities	O
,	O
also	O
known	O
as	O
Stagefright	B-Application
2.0	O
.	O
</s>
<s>
This	O
vulnerability	O
affects	O
specially	O
crafted	O
MP3	O
and	O
MP4	O
files	O
that	O
execute	O
their	O
payload	O
when	O
played	O
using	O
the	O
Android	B-Application
Media	O
server	O
.	O
</s>
<s>
The	O
vulnerability	O
has	O
been	O
assigned	O
identifier	O
and	O
was	O
found	O
in	O
a	O
core	O
Android	B-Application
library	O
called	O
libutils	O
;	O
a	O
component	O
of	O
Android	B-Application
that	O
has	O
existed	O
since	O
Android	B-Application
was	O
first	O
released	O
.	O
</s>
<s>
Android	B-Application
1.5	I-Application
through	O
5.1	O
are	O
vulnerable	O
to	O
this	O
new	O
attack	O
and	O
it	O
is	O
estimated	O
that	O
one	O
billion	O
devices	O
are	O
affected	O
.	O
</s>
<s>
While	O
Google	B-Application
maintains	O
the	O
Android	B-Application
's	O
primary	O
codebase	B-General_Concept
and	O
firmware	B-Application
,	O
updates	O
for	O
various	O
Android	B-Application
devices	O
are	O
the	O
responsibility	O
of	O
wireless	O
carriers	O
and	O
original	O
equipment	O
manufacturers	O
(	O
OEMs	O
)	O
.	O
</s>
<s>
As	O
a	O
result	O
,	O
propagating	O
patches	O
to	O
the	O
actual	O
devices	O
often	O
introduces	O
long	O
delays	O
due	O
to	O
a	O
large	O
fragmentation	O
between	O
the	O
manufacturers	O
,	O
device	O
variants	O
,	O
Android	B-Application
versions	I-Application
,	O
and	O
various	O
Android	B-Application
customizations	O
performed	O
by	O
the	O
manufacturers	O
;	O
furthermore	O
,	O
many	O
older	O
or	O
lower	O
cost	O
devices	O
may	O
never	O
receive	O
patched	O
firmware	B-Application
at	O
all	O
.	O
</s>
<s>
Therefore	O
,	O
the	O
nature	O
of	O
Stagefright	B-Application
bug	B-Error_Name
highlights	O
the	O
technical	O
and	O
organizational	O
difficulties	O
associated	O
with	O
the	O
propagation	O
of	O
Android	B-Application
patches	O
.	O
</s>
<s>
As	O
an	O
attempt	O
to	O
address	O
the	O
delays	O
and	O
issues	O
associated	O
with	O
the	O
propagation	O
of	O
Android	B-Application
patches	O
,	O
on	O
August	O
1	O
,	O
2015	O
Zimperium	O
formed	O
the	O
Zimperium	O
Handset	O
Alliance	O
(	O
ZHA	O
)	O
as	O
an	O
association	O
of	O
different	O
parties	O
interested	O
in	O
exchanging	O
information	O
and	O
receiving	O
timely	O
updates	O
on	O
Android	B-Application
's	O
security-related	O
issues	O
.	O
</s>
<s>
Members	O
of	O
the	O
ZHA	O
also	O
received	O
source	O
code	O
of	O
the	O
Zimperium	O
's	O
proof-of-concept	O
Stagefright	B-Application
exploit	O
before	O
it	O
was	O
publicly	O
released	O
.	O
</s>
<s>
,	O
25	O
of	O
the	O
largest	O
Android	B-Application
device	O
OEMs	O
and	O
wireless	O
carriers	O
have	O
joined	O
the	O
ZHA	O
.	O
</s>
<s>
Certain	O
mitigations	O
of	O
the	O
Stagefright	B-Application
bug	B-Error_Name
exist	O
for	O
devices	O
that	O
run	O
unpatched	O
versions	O
of	O
Android	B-Application
,	O
including	O
disabling	O
the	O
automatic	O
retrieval	O
of	O
MMS	O
messages	O
and	O
blocking	O
the	O
reception	O
of	O
text	O
messages	O
from	O
unknown	O
senders	O
.	O
</s>
<s>
However	O
,	O
these	O
two	O
mitigations	O
are	O
not	O
supported	O
in	O
all	O
MMS	O
applications	O
(	O
the	B-Application
Google	I-Application
Hangouts	B-Protocol
app	O
,	O
for	O
example	O
,	O
only	O
supports	O
the	O
former	O
)	O
,	O
and	O
they	O
do	O
not	O
cover	O
all	O
feasible	O
attack	O
vectors	O
that	O
make	O
exploitation	O
of	O
the	O
Stagefright	B-Application
bug	B-Error_Name
possible	O
by	O
other	O
means	O
,	O
such	O
as	O
by	O
opening	O
or	O
downloading	O
a	O
malicious	O
multimedia	O
file	O
using	O
the	O
device	O
's	O
web	B-Application
browser	I-Application
.	O
</s>
<s>
At	O
first	O
it	O
was	O
thought	O
that	O
further	O
mitigation	O
could	O
come	O
from	O
the	O
address	O
space	O
layout	O
randomization	O
(	O
ASLR	O
)	O
feature	O
that	O
was	O
introduced	O
in	O
Android	B-Application
4.0	O
"	O
Ice	B-Application
Cream	I-Application
Sandwich	I-Application
"	O
,	O
fully	O
enabled	O
in	O
Android	B-Application
4.1	O
"	O
Jelly	B-Application
Bean	I-Application
"	O
;	O
The	O
version	O
of	O
Android	B-Application
5.1	O
"	O
Lollipop	B-Application
"	O
includes	O
patches	O
against	O
the	O
Stagefright	B-Application
bug	B-Error_Name
.	O
</s>
<s>
As	O
of	O
Android	B-Application
10	O
,	O
software	B-General_Concept
codecs	I-General_Concept
were	O
moved	O
to	O
a	O
sandbox	O
which	O
effectively	O
mitigates	O
this	O
threat	O
for	O
devices	O
capable	O
of	O
running	O
this	O
version	O
of	O
the	O
OS	O
.	O
</s>
