CVE-2025-56425: enaio AppConnector SMTP Injection Vulnerability

CVE-2025-56425 Overview

An SMTP command injection vulnerability has been discovered in the AppConnector component of enaio, an enterprise content management platform developed by Optimal Systems. The vulnerability affects multiple versions of enaio (10.10, 11.0, and 11.10) and allows authenticated remote attackers to inject arbitrary SMTP commands through the /osrest/api/organization/sendmail endpoint. By exploiting this flaw, attackers can manipulate email functionality, potentially enabling phishing attacks, spam relay abuse, or unauthorized information disclosure through manipulated email communications.

Critical Impact

Authenticated attackers can inject arbitrary SMTP commands, potentially enabling email spoofing, spam relay abuse, and exfiltration of sensitive data through compromised email functionality.

Affected Products

• enaio 10.10 with AppConnector component version 10.10.0.183 and earlier
• enaio 11.0 with AppConnector component version 11.0.0.183 and earlier
• enaio 11.10 with AppConnector component version 11.10.0.183 and earlier

Discovery Timeline

• 2026-01-08 - CVE-2025-56425 published to NVD
• 2026-01-08 - Last updated in NVD database

Technical Details for CVE-2025-56425

Vulnerability Analysis

This vulnerability represents an SMTP command injection flaw in the enaio AppConnector component. The /osrest/api/organization/sendmail API endpoint fails to properly sanitize user-supplied input before incorporating it into SMTP commands sent to the mail server. Authenticated remote attackers can exploit this weakness by crafting malicious input that includes SMTP protocol commands, effectively breaking out of the intended email context and executing arbitrary SMTP operations.

SMTP injection vulnerabilities occur when applications construct email messages by directly concatenating user input into SMTP command sequences without adequate validation. This allows attackers to inject newline characters followed by additional SMTP commands, manipulating the email flow in unintended ways.

Root Cause

The root cause of this vulnerability is improper input validation and insufficient sanitization of user-controlled data within the sendmail functionality. The AppConnector component does not adequately filter or escape special characters (particularly CRLF sequences) in the input parameters before passing them to the underlying SMTP implementation. This allows attackers to inject arbitrary SMTP commands by inserting line breaks and additional protocol commands into email-related fields.

Attack Vector

The attack is conducted remotely over the network through the REST API endpoint /osrest/api/organization/sendmail. An authenticated attacker can craft HTTP requests containing malicious payloads with embedded SMTP commands. When the vulnerable application processes these requests, the injected commands are executed by the mail server.

Typical attack scenarios include:

• Injecting additional recipients (RCPT TO commands) to redirect emails
• Manipulating email headers to conduct spoofing attacks
• Using the compromised mail server as an open relay for spam distribution
• Exfiltrating sensitive information through manipulated email destinations

The vulnerability requires authentication, meaning the attacker must have valid credentials to access the affected API endpoint. For more technical details, see the Mind-Bytes CVE-2025-56425 Analysis.

Detection Methods for CVE-2025-56425

Indicators of Compromise

• Unusual SMTP traffic patterns originating from the enaio AppConnector server
• Unexpected email recipients or email addresses in mail server logs
• HTTP requests to /osrest/api/organization/sendmail containing CRLF sequences (%0d%0a or \r\n)
• Mail server logs showing injected SMTP commands or unexpected protocol sequences

Detection Strategies

• Monitor HTTP request logs for the /osrest/api/organization/sendmail endpoint, specifically looking for encoded newline characters or suspicious payload patterns
• Implement web application firewall (WAF) rules to detect and block CRLF injection attempts in API requests
• Configure mail server logging to capture full SMTP sessions and analyze for unexpected command sequences
• Deploy endpoint detection solutions to identify anomalous process behavior related to email functionality

Monitoring Recommendations

• Enable detailed logging for all API calls to the sendmail endpoint, including request bodies and headers
• Set up alerts for unusual volumes of outbound email traffic or emails to previously unseen external domains
• Monitor authentication logs for the enaio platform to identify potentially compromised accounts being used for exploitation
• Review mail server relay configurations and logs regularly for signs of abuse

How to Mitigate CVE-2025-56425

Immediate Actions Required

• Update the AppConnector component to the latest patched version for your enaio installation
• Restrict access to the /osrest/api/organization/sendmail endpoint to only necessary users and roles
• Implement network segmentation to limit access to the enaio server and associated mail infrastructure
• Review and audit user accounts with access to the sendmail functionality for any signs of compromise

Patch Information

Organizations should apply the latest security updates from Optimal Systems for the enaio AppConnector component. Consult the Optimal Systems ENAIO website for official patch information and updated component versions that address this vulnerability. It is recommended to upgrade beyond the vulnerable versions:

• AppConnector versions after 10.10.0.183 for enaio 10.10
• AppConnector versions after 11.0.0.183 for enaio 11.0
• AppConnector versions after 11.10.0.183 for enaio 11.10

Workarounds

• Implement input validation at the application gateway level to strip or reject CRLF sequences in API requests
• Apply WAF rules to block requests containing SMTP injection patterns targeting the sendmail endpoint
• Temporarily disable or restrict access to the /osrest/api/organization/sendmail endpoint until patches can be applied
• Configure the mail server to only accept connections from the enaio server and implement strict relay controls

# Example: Block CRLF patterns in web server configuration (Apache)
# Add to virtual host or .htaccess configuration
RewriteEngine On
RewriteCond %{QUERY_STRING} (%0d|%0a|%0D|%0A) [NC]
RewriteRule ^/osrest/api/organization/sendmail - [F,L]