CVE-2025-8066

Executive Summary

CVE-2025-8066 is an open redirect vulnerability affecting Bunker Web version 1.6.2, a component of the Bunkerity security stack running on Linux. This flaw allows an attacker to craft a URL that, when clicked by a victim, redirects them to an untrusted external site. The primary risk is phishing, where a legitimate-looking Bunker Web URL is used to lure users into visiting a malicious site for credential harvesting or malware delivery.

The vulnerability has a CVSS base score of 4.7 (Medium) due to low attack complexity, no privileges required, but requiring user interaction. No public proof-of-concept (PoC) or exploit code is currently available, and the patch status remains unknown. The EPSS score is 0.0%, indicating no active exploitation in the wild at the time of analysis.

Supply Chain & Package Security

This vulnerability is not in a package manager ecosystem (NPM, PyPI, Go, Ruby). It affects a standalone Linux application (Bunker Web) distributed by Bunkerity. Supply chain risk is limited to the integrity of the vendor's distribution channels.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Network (N) – Exploitable remotely.
• Attack Complexity (AC): Low (L) – No special conditions required.
• Privileges Required (PR): None (N) – No authentication needed.
• User Interaction (UI): Required (R) – Victim must click the crafted link.
• Scope (S): Changed (C) – Redirect changes the security context to an external domain.
• Confidentiality (C): Low (L) – Potential for credential theft via phishing.
• Integrity (I): Low (L) – Redirected content may be malicious.
• Availability (A): None (N) – No impact on availability.

Threat Level: Medium. While the impact is limited to phishing, the low complexity and network attack vector make it a viable tool for social engineering campaigns.

Deep Dive & Mechanics

The vulnerability is an Open Redirect (CWE-601) in Bunker Web 1.6.2. The application likely accepts a redirect or next parameter in the URL (e.g., /login?redirect=https://evil.com) without proper validation. When the user completes an action (e.g., login), the application redirects the browser to the specified URL.

Attack Flow:

1. Attacker crafts a URL: https://legitimate-bunker-web.com/login?redirect=https://phishing-site.com
2. Victim clicks the link (e.g., via email or social media).
3. Bunker Web processes the request and redirects the victim to https://phishing-site.com.
4. The victim sees a page that mimics the legitimate login, potentially entering credentials.

Root Cause: Insufficient validation of the redirect target. The application does not check if the target domain is whitelisted or relative.

Vulnerable vs. Patched Code

Since no patch is available, the vulnerable code pattern is inferred:

Vulnerable (Bunker Web 1.6.2):

# Example vulnerable handler
def handle_login(request):
    redirect_url = request.GET.get('redirect', '/dashboard')
    # No validation of redirect_url
    return redirect(redirect_url)

Patched (Hypothetical):

# Example patched handler
import re
ALLOWED_DOMAINS = ['bunkerity.com', 'app.bunkerweb.io']

def handle_login(request):
    redirect_url = request.GET.get('redirect', '/dashboard')
    # Validate redirect URL
    if not is_safe_redirect(redirect_url, ALLOWED_DOMAINS):
        redirect_url = '/dashboard'
    return redirect(redirect_url)

def is_safe_redirect(url, allowed_domains):
    # Check if URL is relative or points to an allowed domain
    if url.startswith('/'):
        return True
    parsed = urlparse(url)
    return parsed.netloc in allowed_domains

Exploitation & Lab Setup

Red Team (Exploitation)

Lab Setup:

1. Install Bunker Web 1.6.2 on a Linux VM (e.g., Ubuntu 22.04).
2. Configure a basic login page.
3. Use a public IP or domain for testing.

Exploitation Steps:

1. Identify the redirect parameter (e.g., redirect, next, url).
2. Craft a malicious URL:

   http://<target-bunker-web>/login?redirect=http://evil.com
   

3. Send the link to a victim via phishing email.
4. Victim clicks, gets redirected to http://evil.com.

No exploit code is available from Exploit-DB.

Blue Team (Detection & Defense)

Detection:

• Monitor logs for unusual redirect parameters pointing to external domains.
• Use web application firewalls (WAF) to block open redirect patterns.

Defense:

• Implement a whitelist of allowed redirect domains.
• Validate that redirect URLs are relative paths only.
• Use HTTP headers like Content-Security-Policy: form-action 'self' to limit form submissions.

Indicators of Compromise (IOCs)

• URL Pattern: */login?redirect=http://* or */login?redirect=https://* (external domains)
• Log Entry: GET /login?redirect=http://evil.com with HTTP 302 response
• Network Traffic: Outbound connections to untrusted domains immediately after a login request

Detection Engineering

YARA Rule

rule CVE_2025_8066_Open_Redirect {
    meta:
        description = "Detects open redirect attempts in Bunker Web logs"
        author = "Valters IT"
        date = "2025-04-10"
        cve = "CVE-2025-8066"
    strings:
        $redirect_param = /[?&](redirect|next|url)=https?:\/\// nocase
        $bunker_web = "Bunker Web" nocase
    condition:
        $redirect_param and $bunker_web
}

Sigma Rule

title: CVE-2025-8066 Open Redirect in Bunker Web
id: 8a9b3c2d-1e5f-4a7b-9c8d-0e1f2a3b4c5d
status: experimental
description: Detects open redirect attempts via redirect parameter in Bunker Web logs
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
    service: access_log
detection:
    selection:
        cs-uri-query|contains: 
            - "redirect=http://"
            - "redirect=https://"
            - "next=http://"
            - "next=https://"
    condition: selection
falsepositives:
    - Legitimate external redirects if whitelisted
level: medium

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-8066 Open Redirect in Bunker Web"; flow:to_server,established; content:"GET"; http_method; content:"/login"; http_uri; pcre:"/[?&](redirect|next|url)=https?:\/\//Ui"; classtype:attempted-recon; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Upgrade: Check for a patched version from Bunkerity. If unavailable, consider disabling the redirect functionality.
2. WAF Rules: Deploy a WAF rule to block requests with external redirect parameters.
3. Input Validation: Manually patch the application to validate redirect URLs against a whitelist.

Long-Term Fix:

• Implement a strict redirect validation function that only allows relative paths or a predefined list of trusted domains.
• Use HTTP security headers (e.g., X-Frame-Options, Content-Security-Policy) to reduce phishing impact.

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