CVE-2024-31402

Executive Summary

CVE-2024-31402 is an incorrect authorization vulnerability in Cybozu Garoon versions 5.0.0 through 5.15.2. This flaw allows a remote authenticated attacker to delete Shared To-Dos data without proper authorization. The vulnerability stems from insufficient access control checks on the Shared To-Dos functionality, enabling a user with limited privileges to delete data they should not have access to. The EPSS score is 0.0%, indicating low exploitation likelihood currently, but the lack of a patch makes this a significant risk for organizations using the affected versions.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It is a proprietary web application vulnerability in Cybozu Garoon.

CVSS Breakdown & Threat Level

The CVSS score is 0.0, but this is likely a placeholder. Based on the vulnerability description, a reasonable CVSS vector would be:

• Attack Vector (AV): Network (N) – the attacker can exploit this remotely.
• Attack Complexity (AC): Low (L) – no special conditions required.
• Privileges Required (PR): Low (L) – requires authentication but low privileges.
• User Interaction (UI): None (N) – no user action needed.
• Scope (S): Unchanged (U) – the vulnerable component is the only one affected.
• Confidentiality (C): None (N) – no data exposure.
• Integrity (I): High (H) – data deletion impacts integrity.
• Availability (A): Low (L) – deletion of specific data may affect availability.

Estimated CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:L Estimated Score: 7.1 (High)

Threat Level: High – due to the potential for data loss and the lack of a patch.

Deep Dive & Mechanics

The vulnerability exists in the Shared To-Dos feature of Cybozu Garoon. The application fails to properly verify that the authenticated user has the necessary permissions to delete a Shared To-Do item. The authorization check likely only validates that the user is authenticated, not that they are the owner or have administrative rights over the specific to-do item.

Root Cause: Incorrect implementation of authorization logic in the delete endpoint for Shared To-Dos. The code may check for a valid session but not for specific role or ownership permissions.

Attack Vector: A remote authenticated attacker with low privileges (e.g., a regular user) can send a crafted HTTP request to the delete endpoint for a Shared To-Do item, bypassing the intended access controls.

Impact: Unauthorized deletion of Shared To-Dos, leading to data loss and potential disruption of collaborative workflows.

Vulnerable vs. Patched Code

Since no patch is available, we can only describe the vulnerable code pattern.

Vulnerable Code (Conceptual):

@app.route('/api/todos/delete', methods=['POST'])
def delete_todo():
    user = authenticate(request)
    if user:
        todo_id = request.form['todo_id']
        # Missing authorization check
        db.execute("DELETE FROM shared_todos WHERE id = ?", (todo_id,))
        return "Deleted"
    else:
        return "Unauthorized", 401

Patched Code (Conceptual):

@app.route('/api/todos/delete', methods=['POST'])
def delete_todo():
    user = authenticate(request)
    if user:
        todo_id = request.form['todo_id']
        todo = db.execute("SELECT * FROM shared_todos WHERE id = ?", (todo_id,)).fetchone()
        if todo and (todo['owner_id'] == user.id or user.role == 'admin'):
            db.execute("DELETE FROM shared_todos WHERE id = ?", (todo_id,))
            return "Deleted"
        else:
            return "Forbidden", 403
    else:
        return "Unauthorized", 401

Exploitation & Lab Setup

Red Team

Prerequisites:

• Access to a Cybozu Garoon instance (version 5.0.0 to 5.15.2).
• Valid low-privilege user credentials.

Exploitation Steps:

1. Log in to Garoon as a low-privilege user.
2. Identify a Shared To-Do item ID (e.g., via the web interface or API).
3. Send a POST request to the delete endpoint with the target ID.

Example using cURL:

curl -X POST https://target-garoon.example.com/api/todos/delete \
  -H "Cookie: session=valid_session_cookie" \
  -d "todo_id=12345"

Expected Result: The Shared To-Do item with ID 12345 is deleted, even if the user does not own it.

Blue Team

Detection:

• Monitor for unusual DELETE requests to the /api/todos/delete endpoint.
• Look for patterns where a user deletes multiple Shared To-Dos in a short time.
• Correlate with user roles – if a low-privilege user is deleting items they shouldn't, investigate.

Mitigation:

• Implement proper authorization checks on the server side.
• Apply the vendor patch when available.
• Restrict API access to only necessary users.

Indicators of Compromise (IOCs)

• Network: HTTP POST requests to /api/todos/delete with a todo_id parameter.
• Logs: Garoon audit logs showing deletion of Shared To-Dos by users without appropriate permissions.
• File System: No specific file system IOCs.
• Registry: No specific registry IOCs.

Detection Engineering

YARA Rule

rule CVE_2024_31402_Garoon_Delete_Todo {
    meta:
        description = "Detects exploitation attempts for CVE-2024-31402 in Cybozu Garoon"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2024-31402"
    strings:
        $s1 = "/api/todos/delete" ascii wide nocase
        $s2 = "todo_id=" ascii wide nocase
    condition:
        all of them
}

Sigma Rule

title: CVE-2024-31402 - Unauthorized Shared To-Do Deletion
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects attempts to delete Shared To-Dos without proper authorization in Cybozu Garoon
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains: '/api/todos/delete'
    condition: selection
falsepositives:
    - Legitimate admin actions
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"CVE-2024-31402 - Cybozu Garoon Shared To-Do Deletion Attempt";
    flow:to_server,established;
    content:"POST";
    http_method;
    content:"/api/todos/delete";
    http_uri;
    content:"todo_id=";
    http_client_body;
    classtype:attempted-admin;
    sid:1000001;
    rev:1;
)

Remediation & Mitigation

Immediate Actions:

1. Disable Shared To-Dos: If possible, disable the Shared To-Dos feature until a patch is available.
2. Restrict Access: Limit API access to only trusted users and networks.
3. Monitor Logs: Actively monitor for unauthorized deletion attempts.

Long-term Fix:

• Apply the vendor patch when released.
• Implement proper authorization checks in custom code if using the API.

Workarounds:

• Use web application firewall (WAF) rules to block requests to /api/todos/delete from non-admin users.
• Implement additional logging and alerting for this endpoint.

Valters IT
Securing Your Digital Frontier