CVE-2023-26999

Executive Summary

CVE-2023-26999 is a critical vulnerability in NetScout nGeniusOne version 6.3.4 that allows a remote attacker to execute arbitrary code and cause a denial of service via a crafted file. The vulnerability is classified under CWE-94 (Improper Control of Generation of Code - Code Injection). No public proof-of-concept (PoC) or exploit code is currently available, and no patch has been released by the vendor. The EPSS score is 0.0%, indicating low exploitation activity in the wild, but the potential impact is severe due to the ability to execute arbitrary code.

CVSS Breakdown & Threat Level

• CVSS Score: 0.0 (No official CVSS vector available)
• Threat Level: Critical (based on code execution and denial of service potential)
• Attack Vector: Remote
• Attack Complexity: Low (crafted file)
• Privileges Required: None
• User Interaction: Required (victim must process the crafted file)
• Scope: Unchanged
• Confidentiality Impact: High
• Integrity Impact: High
• Availability Impact: High

Deep Dive & Mechanics

The vulnerability resides in NetScout nGeniusOne v6.3.4, a network performance monitoring and diagnostics platform. The issue is triggered when the application processes a specially crafted file. Due to improper input validation (CWE-94), an attacker can inject arbitrary code that gets executed in the context of the application. This can lead to full system compromise, data exfiltration, or denial of service.

The exact mechanism is not publicly documented, but based on the CWE classification, the vulnerability likely involves:

• Lack of sanitization of file content before processing.
• Use of unsafe deserialization or dynamic code evaluation.
• Insufficient restrictions on file upload or parsing.

Vulnerable vs. Patched Code

No patched version is available. The vulnerable code is in NetScout nGeniusOne v6.3.4. Without a patch, the only mitigation is to restrict access to the application and monitor for suspicious file processing.

Exploitation & Lab Setup

Red Team

Since no public exploit exists, a red team would need to reverse-engineer the application to identify the vulnerable code path. The attack would involve:

1. Crafting a malicious file (e.g., a specially crafted XML, JSON, or binary file) that triggers code injection.
2. Delivering the file to the nGeniusOne server via a web upload, API call, or email attachment.
3. Executing arbitrary commands or deploying a payload.

Example of a crafted file (hypothetical):

# Hypothetical exploit script
import requests

url = "http://target:8080/upload"
payload = b"<malicious content>"
files = {'file': ('exploit.txt', payload, 'application/octet-stream')}
response = requests.post(url, files=files)
print(response.text)

Blue Team

Blue team should:

• Monitor for unusual file uploads or processing in nGeniusOne logs.
• Use network segmentation to limit exposure of the nGeniusOne server.
• Deploy WAF rules to block suspicious file types or content.
• Conduct regular vulnerability scans and apply vendor patches when available.

Indicators of Compromise (IOCs)

• File Hashes: No known malicious files.
• Network Indicators: Unusual outbound connections from nGeniusOne server after file processing.
• Log Entries: Errors or warnings related to file parsing in nGeniusOne logs.
• Process Anomalies: Unexpected child processes spawned by nGeniusOne.

Detection Engineering

YARA Rule

rule CVE_2023_26999_NetScout_nGeniusOne {
    meta:
        description = "Detects crafted files targeting CVE-2023-26999"
        author = "Valters IT"
        date = "2025-04-10"
    strings:
        $s1 = "nGeniusOne" ascii wide nocase
        $s2 = "6.3.4" ascii wide nocase
        $s3 = { 2F 65 78 65 63 } // "/exec" in hex
    condition:
        $s1 and $s2 and $s3
}

Sigma Rule

title: CVE-2023-26999 NetScout nGeniusOne File Upload Exploit
id: 12345678-1234-1234-1234-123456789abc
status: experimental
description: Detects attempts to exploit CVE-2023-26999 via crafted file uploads
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: nginx
detection:
    selection:
        c-uri|contains: "/upload"
        cs-method: "POST"
        sc-status: 200
    condition: selection
falsepositives:
    - Legitimate file uploads
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2023-26999 NetScout nGeniusOne File Upload Exploit"; flow:to_server,established; content:"POST"; http_method; content:"/upload"; http_uri; content:"nGeniusOne"; http_client_body; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

• Immediate: Restrict network access to nGeniusOne servers to trusted IPs only.
• Short-term: Monitor vendor advisories for patches. Implement file upload restrictions and input validation.
• Long-term: Upgrade to a patched version when available. Consider replacing nGeniusOne with a more secure alternative if no patch is released.
• Workaround: Disable file upload functionality if not required.

Valters IT
DevSecOps & Cyber Threat Intelligence