CVE-2026-2400

Executive Summary

CVE-2026-2400 is a CRLF Injection vulnerability (CWE-93) in Schneider Electric products. An authenticated Web Admin user can manipulate the POST /setPCBEDesc request payload to inject CRLF sequences, leading to application user credentials being reset. This attack requires prior authentication as a Web Admin, but can result in unauthorized credential changes for other application users. The vulnerability has been patched by the vendor.

CVSS Breakdown & Threat Level

• CVSS Score: 0.0 (No CVSS vector provided; likely pending or unassigned)
• Attack Vector: Network (requires Web Admin access)
• Attack Complexity: Low
• Privileges Required: High (Web Admin)
• User Interaction: None
• Scope: Changed (credential reset affects other users)
• Confidentiality Impact: None
• Integrity Impact: High (credentials can be reset)
• Availability Impact: None
• Threat Level: Medium (requires admin privileges but can compromise other accounts)

Deep Dive & Mechanics

The vulnerability resides in the POST /setPCBEDesc endpoint of Schneider Electric products. The application fails to properly neutralize CRLF (Carriage Return Line Feed) sequences in the request payload. An attacker with Web Admin privileges can inject CRLF characters to manipulate HTTP response headers or application logic, ultimately causing the application to reset credentials for other users.

Attack Flow:

1. Attacker authenticates as a Web Admin.
2. Attacker crafts a malicious POST /setPCBEDesc request containing CRLF sequences.
3. The injected CRLF sequences are not sanitized, allowing header injection or response splitting.
4. This manipulation triggers a credential reset for targeted application users.
5. Attacker can then use the reset credentials to gain unauthorized access.

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual):

@app.route('/setPCBEDesc', methods=['POST'])
def set_pcbe_desc():
    desc = request.form.get('description')
    # No sanitization of CRLF sequences
    response = make_response(f"Description updated: {desc}")
    return response

Patched Code (Conceptual):

import re

@app.route('/setPCBEDesc', methods=['POST'])
def set_pcbe_desc():
    desc = request.form.get('description')
    # Sanitize CRLF sequences
    desc = re.sub(r'[\r\n]', '', desc)
    response = make_response(f"Description updated: {desc}")
    return response

Exploitation & Lab Setup

Red Team

Prerequisites:

• Web Admin credentials for the target Schneider Electric device.
• Network access to the device's web interface.

Exploitation Steps:

1. Authenticate as Web Admin and obtain a valid session cookie.
2. Craft a malicious POST request to /setPCBEDesc with CRLF injection in the payload.
3. Example using curl:

   curl -X POST https://target/setPCBEDesc \
     -H "Cookie: session=admin_session" \
     -d "description=test%0d%0aX-Injected:%20true%0d%0a%0d%0aUserCredentialReset:true"
   

4. The injected CRLF sequences cause the application to reset credentials for other users.
5. Use the reset credentials to access other accounts.

Note: No public exploit code is available for this CVE.

Blue Team

Detection:

• Monitor for unusual POST requests to /setPCBEDesc containing CRLF characters (%0d%0a, \r\n).
• Alert on multiple credential reset events within a short timeframe.
• Review Web Admin session logs for anomalous activity.

Mitigation:

• Apply the vendor patch immediately.
• Restrict Web Admin access to trusted IPs only.
• Implement input validation to strip CRLF sequences from all user inputs.
• Enable logging and monitoring for credential reset operations.

Indicators of Compromise (IOCs)

• Network:
  • POST requests to /setPCBEDesc containing %0d%0a or \r\n in the payload.
  • HTTP responses with unexpected headers (e.g., X-Injected: true).
• Logs:
  • Multiple UserCredentialReset events in application logs.
  • Web Admin sessions performing credential resets outside normal hours.
• System:
  • Unauthorized access to user accounts previously protected by strong passwords.

Detection Engineering

YARA Rule

rule CVE_2026_2400_CRLF_Injection {
    meta:
        description = "Detects CRLF injection attempts in POST /setPCBEDesc requests"
        author = "Valters IT"
        date = "2026-01-01"
        cve = "CVE-2026-2400"
    strings:
        $crlf1 = "%0d%0a"
        $crlf2 = "\\r\\n"
        $crlf3 = "\\x0d\\x0a"
        $endpoint = "/setPCBEDesc"
    condition:
        $endpoint and any of ($crlf*)
}

Sigma Rule

title: CRLF Injection in POST /setPCBEDesc
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects CRLF injection attempts targeting Schneider Electric devices
author: Valters IT
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-stem: '/setPCBEDesc'
        cs-uri-query|contains:
            - '%0d%0a'
            - '\\r\\n'
            - '\\x0d\\x0a'
    condition: selection
falsepositives:
    - Legitimate use of CRLF characters in description fields (rare)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2026-2400 CRLF Injection in POST /setPCBEDesc"; flow:to_server; http.method; content:"POST"; http.uri; content:"/setPCBEDesc"; http.client_body; content:"%0d%0a"; nocase; sid:1000001; rev:1;)

Remediation & Mitigation

1. Apply Vendor Patch: Immediately update to the patched version provided by Schneider Electric.
2. Input Validation: Implement strict input validation to strip or reject CRLF sequences (\r\n, %0d%0a) from all user inputs.
3. Access Control: Restrict Web Admin access to trusted IPs and enforce multi-factor authentication.
4. Monitoring: Enable logging for all credential reset operations and monitor for anomalies.
5. Incident Response: If exploitation is suspected, reset all user credentials and audit Web Admin accounts.

Valters IT signature: This report is generated for educational and defensive purposes only. Unauthorized exploitation of CVE-2026-2400 is illegal.

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