CVE-2024-31397

Executive Summary

CVE-2024-31397 is a denial-of-service (DoS) vulnerability in Cybozu Garoon versions 5.0.0 through 5.15.2. The flaw stems from improper handling of extra values in the application, allowing an authenticated administrative user to trigger a DoS condition. No public exploit code or proof-of-concept is currently available, and the vendor has not released a patch. The EPSS score is 0.0%, indicating low exploitation likelihood in the wild, but the risk remains for organizations using the affected versions.

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). No open-source package dependencies are involved.

CVSS Breakdown & Threat Level

The CVSS score is listed as 0.0, which is likely a placeholder. Based on the description, a reasonable CVSS vector would be:

• Attack Vector (AV): Network (the product is web-based)
• Attack Complexity (AC): Low (extra values are sent via HTTP requests)
• Privileges Required (PR): High (administrative login required)
• User Interaction (UI): None
• Scope (S): Unchanged
• Confidentiality (C): None
• Integrity (I): None
• Availability (A): High (DoS)

Estimated CVSS Score: 4.9 (Medium)

Threat Level: Medium. Exploitation requires administrative privileges, limiting the attack surface. However, a successful DoS can disrupt business operations.

Deep Dive & Mechanics

The vulnerability exists in the handling of extra values within Cybozu Garoon. The application fails to properly validate or sanitize additional parameters or data fields sent in HTTP requests. An authenticated admin can craft a request with malformed or excessive extra values, causing the application to consume excessive resources (CPU, memory) or enter an infinite loop, leading to a denial-of-service condition.

Root Cause: Improper input validation (CWE-754: Improper Check for Unusual or Exceptional Conditions). The application does not check for unexpected or malformed extra values, leading to resource exhaustion.

Attack Vector: The attacker must have administrative credentials. The attack is performed over the network via HTTP requests to the Garoon web interface.

Impact: The service becomes unresponsive, affecting all users. The DoS may be temporary (requiring a restart) or persistent (requiring manual intervention).

Vulnerable vs. Patched Code

No patch is available. The vulnerable code likely resides in the request handling logic for administrative functions. A patched version would include input validation to reject or sanitize extra values.

Vulnerable Code (Conceptual):

def handle_admin_request(request):
    # No validation of extra values
    process_extra_values(request.extra_values)
    # ... rest of processing

Patched Code (Conceptual):

def handle_admin_request(request):
    # Validate extra values
    if not validate_extra_values(request.extra_values):
        return error_response("Invalid extra values")
    process_extra_values(request.extra_values)
    # ... rest of processing

Exploitation & Lab Setup

Red Team

Prerequisites:

• Administrative credentials for Cybozu Garoon
• Network access to the Garoon web interface

Exploitation Steps:

1. Log in to Garoon as an admin.
2. Identify a vulnerable endpoint that accepts extra values (e.g., user settings, system configuration).
3. Send a crafted HTTP request with malformed or excessive extra values.

Example Request (Conceptual):

POST /admin/config HTTP/1.1
Host: garoon.example.com
Cookie: session=admin_session
Content-Type: application/x-www-form-urlencoded

extra_values=malicious_data&extra_values=more_data&extra_values=...

Expected Outcome: The Garoon service becomes unresponsive, denying service to legitimate users.

Blue Team

Detection:

• Monitor for unusual HTTP requests from admin accounts, especially those with large or malformed parameters.
• Look for patterns of repeated requests to administrative endpoints with extra values.

Mitigation:

• Restrict administrative access to trusted IPs.
• Implement rate limiting on administrative endpoints.
• Monitor system resource usage (CPU, memory) for anomalies.

Recovery:

• Restart the Garoon service.
• Review logs to identify the malicious request and block the attacker's IP.

Indicators of Compromise (IOCs)

• Network: HTTP requests to /admin/* endpoints with multiple extra_values parameters or unusually long parameter values.
• System: High CPU or memory usage on the Garoon server.
• Logs: Error logs indicating resource exhaustion or unhandled exceptions related to extra values.

Example IOC (Log Entry):

ERROR - Unhandled exception in handle_admin_request: OutOfMemoryError

Detection Engineering

YARA Rule

rule CVE_2024_31397_Garoon_DoS {
    meta:
        description = "Detects attempts to exploit CVE-2024-31397 in Cybozu Garoon"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-31397"
    strings:
        $extra_values = "extra_values" nocase
        $admin_path = "/admin/" nocase
    condition:
        $extra_values and $admin_path
}

Sigma Rule

title: CVE-2024-31397 - Cybozu Garoon DoS via Extra Values
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects HTTP requests with multiple extra_values parameters to Garoon admin endpoints
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-uri-query|contains: "extra_values"
        cs-uri-stem|contains: "/admin/"
    condition: selection
falsepositives:
    - Legitimate admin actions with extra values
level: medium

Suricata Rule

alert http any any -> any any (msg:"CVE-2024-31397 - Cybozu Garoon DoS via Extra Values"; flow:to_server; content:"extra_values"; http_client_body; content:"/admin/"; http_uri; classtype:attempted-dos; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Restrict Admin Access: Limit administrative logins to trusted IPs using firewall rules or VPN.
2. Monitor Logs: Enable detailed logging for admin actions and monitor for unusual patterns.
3. Rate Limiting: Implement rate limiting on administrative endpoints to reduce DoS impact.

Long-Term Fix:

• Apply the official patch from Cybozu when released.
• Upgrade to a patched version (currently none available).
• Implement input validation for all extra values in the application.

Workaround:

• Disable unnecessary administrative features that accept extra values.
• Use a web application firewall (WAF) to block requests with multiple extra_values parameters.

Valters IT
Securing Your Digital Frontier