Attack Chain

1. Initial Access: An attacker obtains valid login credentials for any low-privileged OpenEMR user account.
2. Authentication: The attacker authenticates to the OpenEMR system, establishing a valid session.
3. Vulnerability Exploitation: The attacker sends a specially crafted GET request to the vulnerable endpoint: /interface/modules/custom_modules/oe-module-faxsms/index.php.
4. Parameter Injection: The GET request includes parameters such as type=fax, _ACTION_COMMAND (either disposeDoc or disposeDocument), action=download, and a malicious file_path parameter pointing to a target file on the server's filesystem (e.g., /etc/passwd, /var/www/html/openemr/sites/default/sqlconf.php).
5. Arbitrary File Read: The disposeDoc() method, lacking proper path validation, reads the content of the specified arbitrary file and returns it within the HTTP response body to the attacker.
6. Sensitive Data Exposure: The attacker successfully retrieves sensitive information such as database credentials, API keys, or system configuration details.
7. File Deletion (Optional Impact): If the web server process has write permissions to the targeted file, the disposeDoc() method proceeds to call unlink() on the file, permanently deleting it from the server.
8. Post-Exploitation: The attacker uses the exfiltrated sensitive data for further privilege escalation, lateral movement, or to gain control over the database.

Impact

The successful exploitation of CVE-2026-24849 can lead to severe consequences, including the unauthorized disclosure of highly sensitive data. Attackers can read critical system files like /etc/passwd to enumerate users or sites/default/sqlconf.php to obtain database credentials, compromising patient records or administrative data. The ability to delete files via unlink() poses a risk of data destruction and denial of service if critical application files are targeted and removed. Although the exploit requires authentication, the low privilege level needed means many user accounts could be leveraged. Given OpenEMR's common use in healthcare, a breach could lead to HIPAA violations, significant financial penalties, reputational damage, and loss of patient trust for affected organizations.

Recommendation

• Patch CVE-2026-24849: Immediately upgrade OpenEMR instances to version 7.0.4 or higher to remediate CVE-2026-24849.
• Deploy Sigma Rules: Implement the provided Sigma rules to your SIEM solution and configure web server logging (category webserver) to monitor for exploitation attempts.
• Monitor Web Server Logs: Actively monitor webserver logs for requests to /interface/modules/custom_modules/oe-module-faxsms/index.php containing _ACTION_COMMAND and a file_path parameter, as detailed in the detection rules.
• Review Access Controls: Periodically review and harden file system permissions on your OpenEMR deployment to follow the principle of least privilege, minimizing the impact even if a file read vulnerability is exploited.