CVE-2025-27517

Executive Summary

CVE-2025-27517 is a critical Remote Code Execution (RCE) vulnerability in the Volt package, a functional API for the Livewire framework. The flaw allows an unauthenticated attacker to send specially crafted request payloads to Volt components, leading to arbitrary code execution on the server. This vulnerability affects all versions prior to 1.7.0. Given the CVSS score of 10.0 (Critical) and the lack of public proof-of-concept (PoC) at this time, immediate patching is strongly advised.

Supply Chain & Package Security

This vulnerability affects the Volt package, which is distributed via Composer for PHP projects. Organizations using Livewire with Volt should treat this as a supply chain risk. The package is a direct dependency, and the vulnerable code is executed server-side. Ensure that your composer.json requires "livewire/volt": "^1.7.0" or higher. Verify the integrity of the package by checking the hash against the official repository.

CVSS Breakdown & Threat Level

• CVSS Score: 10.0 (Critical)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
• Attack Vector: Network (AV:N) – The vulnerability can be exploited remotely.
• Attack Complexity: Low (AC:L) – No special conditions are required.
• Privileges Required: None (PR:N) – No authentication needed.
• User Interaction: None (UI:N) – No user action required.
• Scope: Unchanged (S:U) – The vulnerable component and the impacted component are the same.
• Confidentiality Impact: High (C:H) – Full system compromise possible.
• Integrity Impact: High (I:H) – Attacker can modify data and execute code.
• Availability Impact: High (A:H) – Attacker can disrupt service.

Threat Level: Critical. The combination of network exploitability, no authentication, and full system compromise makes this a top-priority vulnerability.

Deep Dive & Mechanics

The vulnerability resides in how Volt processes incoming HTTP request payloads. Volt components, which are PHP classes that handle user interactions, deserialize or evaluate user-supplied data without proper sanitization. An attacker can craft a malicious payload that, when processed by the Volt component, triggers the execution of arbitrary PHP code.

The root cause is likely a deserialization flaw (CWE-502) or an unsafe eval()-like function call. The exact mechanism is not publicly disclosed, but the advisory confirms that user-crafted request payloads can lead to RCE. The fix in version 1.7.0 likely involves stricter input validation, disabling dangerous PHP functions, or using a safe deserialization method.

Vulnerable vs. Patched Code

The following is a hypothetical example based on the vulnerability description. The actual vulnerable code is not public.

Vulnerable Code (Pre-1.7.0):

// VoltComponent.php (vulnerable)
public function handleRequest($payload) {
    // Unsafe deserialization or evaluation
    $data = unserialize($payload);
    // Process $data...
}

Patched Code (1.7.0):

// VoltComponent.php (patched)
public function handleRequest($payload) {
    // Safe JSON parsing with validation
    $data = json_decode($payload, true);
    if (json_last_error() !== JSON_ERROR_NONE) {
        throw new \InvalidArgumentException('Invalid payload');
    }
    // Process $data...
}

The patched version replaces the dangerous unserialize() with json_decode() and adds error checking.

Exploitation & Lab Setup

Red Team (Offensive)

Lab Setup:

1. Deploy a vulnerable Livewire application with Volt < 1.7.0 (e.g., using Docker).
2. Identify a Volt component endpoint (e.g., /livewire/message/component-name).
3. Craft a malicious payload. Since no public PoC exists, the following is a conceptual example:

# Conceptual payload (not tested)
curl -X POST http://target.com/livewire/message/MyComponent \
  -H "Content-Type: application/json" \
  -d '{"component":"MyComponent","payload":"O:8:\"stdClass\":0:{}"}'

Note: The actual payload will depend on the specific deserialization gadget chain available in the PHP environment. Tools like PHPGGC can be used to generate gadget chains for common PHP frameworks.

Blue Team (Defensive)

Detection:

• Monitor for unusual POST requests to Livewire endpoints with non-JSON payloads.
• Look for payloads containing serialized PHP objects (e.g., O:, a:, s:).
• Alert on any unserialize() calls in application logs.

Hunting:

• Search for requests with Content-Type: application/x-www-form-urlencoded or multipart/form-data that contain serialized PHP data.
• Use the Sigma rule below to detect exploitation attempts.

Indicators of Compromise (IOCs)

• Network:
  • POST requests to /livewire/message/* with payloads containing serialized PHP objects.
  • Unusual HTTP headers like X-Livewire-Component with unexpected values.
• File System:
  • Unexpected PHP files in web-accessible directories (e.g., /var/www/html/shell.php).
  • Modified .env or configuration files.
• Process:
  • Unusual PHP processes executing system commands (e.g., php -r 'system("id");').
• Logs:
  • PHP error logs showing unserialize() errors or eval() calls.
  • Web server access logs with 200 responses to Livewire endpoints with large payloads.

Detection Engineering

YARA Rule

rule CVE_2025_27517_Exploit {
    meta:
        description = "Detects serialized PHP objects in HTTP requests targeting Livewire/Volt"
        author = "Valters IT"
        date = "2025-03-01"
        reference = "CVE-2025-27517"
    strings:
        $serialized = /O:\d+:"/
        $livewire_path = /\/livewire\/message\//
    condition:
        $livewire_path and $serialized
}

Sigma Rule

title: CVE-2025-27517 Livewire Volt RCE Attempt
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects attempts to exploit CVE-2025-27517 via serialized PHP objects in Livewire requests
author: Valters IT
date: 2025-03-01
logsource:
    category: webserver
    product: apache
    service: accesslog
detection:
    selection:
        cs-method: 'POST'
        cs-uri-stem|startswith: '/livewire/message/'
        cs-uri-query|contains: 'O:'
    condition: selection
falsepositives:
    - Legitimate serialized data (rare)
level: critical

Suricata Rule

alert http any any -> any any (
    msg:"CVE-2025-27517 Livewire Volt RCE Attempt";
    flow:to_server,established;
    content:"POST";
    http_method;
    content:"/livewire/message/";
    http_uri;
    pcre:"/O:\d+:\"/";
    classtype:attempted-admin;
    sid:1000001;
    rev:1;
    reference:cve,2025-27517;
)

Remediation & Mitigation

Immediate Actions:

1. Patch: Upgrade Volt to version 1.7.0 or later. Run composer require livewire/volt:^1.7.0.
2. Verify: Check that the update is applied by reviewing composer.lock for "livewire/volt" version >= 1.7.0.
3. Monitor: Enable logging for all Livewire endpoints and review for suspicious activity.

Long-term Mitigations:

• Implement a Web Application Firewall (WAF) rule to block serialized PHP objects in POST requests.
• Disable unserialize() in PHP configuration if not needed (disable_functions = unserialize).
• Use input validation and sanitization for all user-supplied data.
• Regularly update all dependencies, especially those handling user input.

Workarounds (if patching is not immediately possible):

• Restrict access to Livewire endpoints via IP whitelisting or VPN.
• Disable the Volt package temporarily by removing it from composer.json and clearing the cache.

Valters IT
Securing Digital Frontiers