CVE-2025-68721

Executive Summary

CVE-2025-68721 is a critical improper access control vulnerability in Axigen Mail Server versions prior to 10.5.57. The flaw resides in the WebAdmin interface, specifically within the SSL Certificates management endpoint (page=sslcerts). A delegated admin account with zero permissions can bypass access control checks and gain unauthorized access to this endpoint. This allows an attacker to view, download, upload, and delete SSL certificate files, effectively compromising the entire TLS/SSL trust chain of the mail server. The vulnerability is classified under CWE-284 (Improper Access Control) and is mapped to MITRE ATT&CK tactic T1190 (Exploit Public-Facing Application). No public proof-of-concept (PoC) or exploit code is currently available, but the risk is high due to the potential for complete compromise of encrypted communications.

CVSS Breakdown & Threat Level

• CVSS Score: 9.9 (Critical)
• Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
• Attack Vector (AV): Network (N) – Exploitable remotely.
• Attack Complexity (AC): Low (L) – No special conditions required.
• Privileges Required (PR): Low (L) – Requires a delegated admin account, even with zero permissions.
• User Interaction (UI): None (N) – No user action needed.
• Scope (S): Unchanged (U) – The vulnerable component remains the same.
• Confidentiality (C): High (H) – Full disclosure of SSL private keys and certificates.
• Integrity (I): High (H) – Attacker can upload malicious certificates, enabling man-in-the-middle attacks.
• Availability (A): High (H) – Attacker can delete certificates, causing denial of service for encrypted connections.

Threat Level: Critical. The vulnerability allows a low-privileged attacker to fully compromise the SSL/TLS infrastructure, leading to data interception, impersonation, and service disruption.

Deep Dive & Mechanics

The vulnerability is a classic case of improper access control (CWE-284) in the Axigen WebAdmin interface. The application fails to enforce proper authorization checks on the page=sslcerts endpoint. While the UI may hide the SSL Certificates management section from delegated admins with zero permissions, the backend does not validate whether the requesting user has the necessary privileges to access this endpoint. This allows an attacker with a valid delegated admin session to directly request the endpoint and perform CRUD operations on SSL certificate files.

Attack Flow:

1. Authentication: The attacker obtains a delegated admin account (e.g., via phishing, credential stuffing, or insider threat). This account has zero permissions assigned.
2. Endpoint Discovery: The attacker navigates to the WebAdmin interface and manually requests the SSL certificates management page: https://target-axigen-server:9000/?page=sslcerts.
3. Bypass: The server does not check the user's permissions for this specific endpoint, allowing access.
4. Exploitation: The attacker can:
   • View/Download: Extract existing SSL certificates and private keys.
   • Upload: Replace legitimate certificates with attacker-controlled ones, enabling man-in-the-middle attacks.
   • Delete: Remove all certificates, causing TLS/SSL connections to fail.

Root Cause: The access control logic is implemented at the UI layer (hiding the menu item) rather than at the server-side authorization layer. This is a common but dangerous oversight.

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual):

// In vulnerable versions, the endpoint does not check permissions.
if ($_GET['page'] == 'sslcerts') {
    // Directly process SSL certificate operations without authorization.
    handleSSLCertificates();
}

Patched Code (Conceptual):

// In patched version 10.5.57, authorization is enforced.
if ($_GET['page'] == 'sslcerts') {
    if (!checkUserPermission('manage_ssl_certs')) {
        die('Access denied: insufficient privileges.');
    }
    handleSSLCertificates();
}

The patch adds a server-side permission check before allowing access to the SSL certificates management functionality. This ensures that only users with the appropriate role (e.g., super admin) can interact with this endpoint.

Exploitation & Lab Setup

Red Team

Lab Setup:

1. Deploy a vulnerable Axigen Mail Server (version < 10.5.57) in a controlled environment.
2. Create a delegated admin account with zero permissions.
3. Access the WebAdmin interface (default port 9000).

Exploitation Steps:

1. Log in with the delegated admin account.
2. Directly navigate to: https://<target>:9000/?page=sslcerts
3. If successful, the SSL certificates management page will load.
4. Use the interface to:
   • Download existing certificates (e.g., server.crt, server.key).
   • Upload a malicious certificate to impersonate the server.
   • Delete all certificates to cause a denial of service.

Example Request (using curl):

# Download a certificate (requires session cookie)
curl -k -X GET "https://target:9000/?page=sslcerts&action=download&file=server.crt" \
  -H "Cookie: sessionid=YOUR_SESSION_COOKIE" \
  -o server.crt

Blue Team

Detection Steps:

1. Monitor WebAdmin access logs for requests to page=sslcerts from non-admin users.
2. Alert on any CRUD operations on SSL certificate files (upload, download, delete).
3. Check for unexpected changes to SSL certificates or private keys.
4. Review delegated admin accounts for any that have been granted excessive permissions.

Hunting Query (Splunk):

index=webadmin_logs source="/var/log/axigen/webadmin.log"
| search "page=sslcerts"
| eval is_admin=if(role="superadmin", "yes", "no")
| where is_admin="no"
| table _time, user, action, file, src_ip

Indicators of Compromise (IOCs)

• Network IOCs:

  • HTTP requests to / with page=sslcerts parameter from non-admin IPs.
  • Unusual file downloads of .crt, .key, .pem files from the WebAdmin interface.
  • Uploads of new certificate files to the server.

• File IOCs:

  • New or modified SSL certificate files in the Axigen certificate directory (e.g., /opt/axigen/certs/).
  • Unexpected changes to certificate file permissions or ownership.

• Log IOCs:

  • WebAdmin access logs showing page=sslcerts accessed by users with role delegated_admin and zero permissions.
  • Audit logs showing certificate operations (upload, delete) performed by unauthorized users.

Detection Engineering

YARA Rule

rule CVE_2025_68721_Axigen_SSL_Bypass {
    meta:
        description = "Detects exploitation attempts of CVE-2025-68721 in Axigen Mail Server logs"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2025-68721"
    strings:
        $s1 = "page=sslcerts" ascii wide nocase
        $s2 = "action=download" ascii wide nocase
        $s3 = "action=upload" ascii wide nocase
        $s4 = "action=delete" ascii wide nocase
    condition:
        any of ($s*) and filesize < 10KB
}

Sigma Rule

title: Axigen WebAdmin SSL Certificate Access by Unauthorized User
id: 8a4b3c2d-1e5f-4a7b-9c8d-0e1f2a3b4c5d
status: experimental
description: Detects access to the SSL certificates management endpoint by users without proper permissions.
author: Valters IT
date: 2025-04-10
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2025-68721
logsource:
    product: axigen
    service: webadmin
detection:
    selection:
        url.query|contains: 'page=sslcerts'
    filter:
        user.role: 'superadmin'
    condition: selection and not filter
falsepositives:
    - Legitimate superadmin access
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"CVE-2025-68721 Axigen WebAdmin SSL Certificate Access Bypass";
    flow:to_server,established;
    content:"page=sslcerts"; http_uri;
    nocase;
    sid:1000001;
    rev:1;
    reference:cve,2025-68721;
    classtype:attempted-admin;
    priority:1;
)

Remediation & Mitigation

Immediate Actions:

1. Upgrade: Update Axigen Mail Server to version 10.5.57 or later immediately.
2. Restrict Access: If immediate patching is not possible, restrict network access to the WebAdmin interface (port 9000) to trusted IPs only.
3. Review Accounts: Audit all delegated admin accounts and revoke any that are unnecessary.

Long-Term Mitigations:

1. Implement Network Segmentation: Place the WebAdmin interface on a separate management VLAN.
2. Enable Multi-Factor Authentication (MFA): Add an extra layer of security for all admin accounts.
3. Monitor Logs: Continuously monitor WebAdmin logs for unauthorized access attempts.
4. Apply Principle of Least Privilege: Ensure that delegated admin accounts have only the permissions necessary for their role.

Workaround (if patching is delayed):

• Use a reverse proxy (e.g., Nginx) to block requests containing page=sslcerts in the URI for non-admin users.
• Example Nginx rule:

location / {
    if ($arg_page = "sslcerts") {
        return 403;
    }
}

Valters IT
Securing Digital Frontiers