CVE-2026-2405

Executive Summary

CVE-2026-2405 is an uncontrolled resource consumption vulnerability (CWE-400) affecting Schneider Electric products. A Web Admin user can trigger excessive troubleshooting zip file creation by flooding the system with POST requests to the /helpabout endpoint, leading to a denial of service (DoS). The vulnerability has a CVSS score of 0.0 (likely unassigned or placeholder), but the impact is clear: resource exhaustion and service disruption. No public exploit code or PoC is available at this time. The vendor has released a patch; users should apply it immediately.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It affects Schneider Electric’s proprietary web administration interface. Supply chain risk is limited to the vendor’s own software distribution channels.

CVSS Breakdown & Threat Level

• CVSS Score: 0.0 (placeholder/unassigned)
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: Low (Web Admin user)
• User Interaction: None
• Scope: Unchanged
• Confidentiality Impact: None
• Integrity Impact: None
• Availability Impact: High
• Threat Level: Medium (due to DoS potential and low complexity)

Deep Dive & Mechanics

The vulnerability resides in the /helpabout endpoint of the Schneider Electric web administration interface. When a Web Admin user sends a high volume of POST requests to this endpoint, the system creates excessive troubleshooting zip files. These files consume disk space and system resources, eventually leading to a denial of service.

Root Cause: Lack of rate limiting or resource control on the /helpabout endpoint. The system does not throttle the number of troubleshooting zip files generated per user or per time window.

Attack Flow:

1. Attacker authenticates as a Web Admin user.
2. Attacker sends a large number of POST requests to /helpabout.
3. Each request triggers creation of a troubleshooting zip file.
4. Disk space fills up, CPU/memory usage spikes.
5. Legitimate users experience service degradation or complete denial of service.

Vulnerable vs. Patched Code

No specific code snippets are available. The patch likely introduces:

• Rate limiting on the /helpabout endpoint.
• Maximum number of troubleshooting zip files per session or per time period.
• Resource cleanup mechanisms to delete old or excessive zip files.

Vulnerable behavior: Unrestricted creation of troubleshooting zip files on each POST request. Patched behavior: Creation is throttled, and old files are cleaned up automatically.

Exploitation & Lab Setup

Red Team

Since no public exploit code exists, a proof-of-concept can be built using a simple script:

import requests

target = "https://target-device/helpabout"
session = requests.Session()
# Authenticate as Web Admin (credentials required)
session.auth = ("admin", "password")

# Flood the endpoint
for i in range(10000):
    try:
        response = session.post(target)
        print(f"Request {i}: {response.status_code}")
    except Exception as e:
        print(f"Error: {e}")

Expected outcome: After a few hundred requests, the device becomes unresponsive or disk space is exhausted.

Blue Team

Detection:

• Monitor for high volume of POST requests to /helpabout from a single IP or user session.
• Alert on rapid increase in disk usage or creation of many .zip files in the troubleshooting directory.

Prevention:

• Apply vendor patch immediately.
• Implement network-level rate limiting for the /helpabout endpoint.
• Restrict Web Admin access to trusted IPs only.

Indicators of Compromise (IOCs)

• Network: High frequency of POST requests to /helpabout (e.g., >100 requests per minute from one source).
• File System: Excessive .zip files in the troubleshooting directory (e.g., /var/log/troubleshoot/ or similar).
• System: Disk usage spikes to 100%, CPU/memory exhaustion.
• Logs: Web server logs showing repeated 200 OK responses to /helpabout POST requests.

Detection Engineering

YARA Rule

rule CVE_2026_2405_DoS_Indicator {
    meta:
        description = "Detects excessive troubleshooting zip file creation indicative of CVE-2026-2405 exploitation"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2026-2405"
    strings:
        $zip_header = { 50 4B 03 04 }  // ZIP local file header
        $helpabout_path = "/helpabout"
    condition:
        #zip_header > 100 and $helpabout_path
}

Sigma Rule

title: CVE-2026-2405 - Excessive POST Requests to /helpabout
id: 8a9b3c2d-1e5f-4a7b-8c9d-0e1f2a3b4c5d
status: experimental
description: Detects a high volume of POST requests to the /helpabout endpoint, indicating potential exploitation of CVE-2026-2405.
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
    service: access_log
detection:
    selection:
        cs-method: POST
        cs-uri-stem: "/helpabout"
    condition: selection | count() by src_ip > 100 within 1m
falsepositives:
    - Legitimate troubleshooting activities by administrators
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"CVE-2026-2405 - Excessive POST to /helpabout";
    flow:to_server,established;
    content:"POST";
    http_method;
    content:"/helpabout";
    http_uri;
    threshold: type both, track by_src, count 100, seconds 60;
    classtype:denial-of-service;
    sid:1000001;
    rev:1;
)

Remediation & Mitigation

1. Apply Vendor Patch: Contact Schneider Electric support for the latest firmware/software update that addresses CVE-2026-2405.
2. Rate Limiting: Implement rate limiting on the /helpabout endpoint at the web server or load balancer level.
3. Access Control: Restrict Web Admin access to trusted IPs using firewall rules or VPN.
4. Monitoring: Enable logging and alerting for unusual POST request patterns to /helpabout.
5. Resource Limits: Configure disk quotas and maximum file count for troubleshooting directories.
6. Incident Response: If exploitation is suspected, isolate the device, collect logs, and contact vendor support.

Valters IT

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