CVE-2026-2400: CRLF Injection Auth Bypass Vulnerability

CVE-2026-2400 Overview

CVE-2026-2400 is a CRLF Injection vulnerability (CWE-93: Improper Neutralization of CRLF Sequences) that affects Schneider Electric products. This vulnerability exists in the web administration interface and could allow an authenticated attacker to reset application user credentials by manipulating the POST /setPCBEDesc request payload with specially crafted CRLF sequences.

Critical Impact

Authenticated attackers can exploit CRLF injection in the /setPCBEDesc endpoint to trigger unintended credential resets, potentially disrupting access for legitimate users and compromising system integrity.

Affected Products

• Schneider Electric Industrial Control Systems (specific product details available in the vendor security advisory)

Discovery Timeline

• 2026-04-14 - CVE CVE-2026-2400 published to NVD
• 2026-04-14 - Last updated in NVD database

Technical Details for CVE-2026-2400

Vulnerability Analysis

This CRLF Injection vulnerability arises from improper neutralization of carriage return (CR, \r) and line feed (LF, \n) characters in user-supplied input. When a Web Admin user interacts with the /setPCBEDesc endpoint, the application fails to properly sanitize the POST request payload. This allows an attacker with administrative privileges to inject CRLF sequences that can manipulate the server's response handling and trigger unintended application behavior, specifically causing user credentials to be reset.

The vulnerability requires the attacker to have authenticated access to the Web Admin interface, which limits the attack surface but still presents significant risk in environments where admin credentials may be compromised or where insider threats exist.

Root Cause

The root cause is insufficient input validation in the /setPCBEDesc endpoint handler. The application does not properly sanitize or reject CRLF sequences (\r\n) within the POST request payload before processing. This allows an attacker to inject additional HTTP headers or manipulate the response structure, leading to the credential reset behavior. Proper encoding or rejection of CRLF characters in user input would prevent this vulnerability.

Attack Vector

The attack is network-based and requires low-privilege authenticated access to the Web Admin interface. An attacker with valid administrative credentials can craft a malicious POST request to the /setPCBEDesc endpoint containing CRLF sequences. These sequences are interpreted by the server, causing unintended modifications to application state that result in user credential resets.

The vulnerability is exploited by injecting CRLF sequences (%0d%0a or \r\n) into the POST /setPCBEDesc request payload. When the server processes this malformed input without proper sanitization, the injected sequences can manipulate the application's internal logic, triggering credential reset functionality. For detailed technical information, refer to the Schneider Electric Security Notice.

Detection Methods for CVE-2026-2400

Indicators of Compromise

• Unusual or unexpected POST requests to the /setPCBEDesc endpoint containing encoded CRLF sequences (%0d%0a, %0D%0A)
• Unexpected user credential resets or authentication failures reported by legitimate users
• Web server logs showing malformed requests with carriage return or line feed characters in POST bodies
• Multiple credential reset events occurring in short time periods without user initiation

Detection Strategies

• Implement web application firewall (WAF) rules to detect and block requests containing CRLF sequences in POST payloads
• Monitor HTTP traffic for encoded newline characters (%0d, %0a, %0D, %0A) in requests to administrative endpoints
• Deploy intrusion detection signatures to identify CRLF injection attempts targeting the /setPCBEDesc endpoint
• Review authentication logs for anomalous credential reset patterns

Monitoring Recommendations

• Enable detailed logging for the web administration interface, capturing full request payloads
• Set up alerts for credential reset events that occur outside of normal administrative procedures
• Monitor for failed authentication attempts following credential reset activities
• Implement anomaly detection for unusual administrative API usage patterns

How to Mitigate CVE-2026-2400

Immediate Actions Required

• Review and apply security patches from Schneider Electric as referenced in the official security advisory
• Restrict network access to the Web Admin interface to trusted management networks only
• Audit Web Admin user accounts and enforce strong authentication mechanisms
• Implement WAF rules to filter CRLF sequences from incoming requests

Patch Information

Schneider Electric has released a security advisory addressing this vulnerability. Organizations should review the Schneider Electric Security Notice (SEVD-2026-104-01) for detailed patch information and remediation guidance. Apply vendor-provided updates as soon as they become available for your specific product version.

Workarounds

• Implement network segmentation to restrict access to the Web Admin interface from untrusted networks
• Deploy a reverse proxy or WAF configured to strip or block CRLF characters from request payloads
• Limit administrative access to essential personnel only and implement additional authentication factors
• Monitor administrative activities and implement session timeout policies to reduce exposure window

# Example WAF rule to block CRLF sequences (ModSecurity format)
SecRule REQUEST_BODY "@rx (%0[dD]|%0[aA]|\r|\n)" \
    "id:100001,phase:2,deny,status:403,msg:'CRLF Injection Attempt Detected'"