Vulnerabilities in the OpenEMR healthcare software could allow remote attackers to steal sensitive patient data or execute arbitrary commands and take over systems.

OpenEMR is an open source software used for the management of health records. It also allows patients to schedule appointments, get in touch with physicians, and pay invoices.

Security researchers at Sonar Source identified and reported three vulnerabilities in OpenEMR, including two that can be chained to achieve remote code execution (RCE).

“A combination of these vulnerabilities allows remote attackers to execute arbitrary system commands on any OpenEMR server and to steal sensitive patient data. In the worst case, they can compromise the entire critical infrastructure,” Sonar warns.

The first of the identified issues is described as an unauthenticated arbitrary file read and exists because the OpenEMR installer does not delete itself after the installation is completed.

Because the installation process is divided into several steps, an unauthenticated attacker could abuse a user-controlled parameter to perform some of these steps (but not a complete setup).

The attacker can invoke a function to read the current theme from the database, which results in a database connection being established using attacker-controlled properties.

A MySQL statement can be used to load the contents of a file to the database table, and a modifier can be supplied so that the file is read from the client instead of the server.

“A malicious server can request the content of another file, even in response to a totally different query from the client,” Sonar notes.

This allows an unauthenticated attacker to use a rogue MySQL server to read OpenEMR files such as backups, certificates, passwords, and tokens.

Sonar also discovered that an attacker could abuse a cross-site scripting (XSS) flaw to execute JavaScript code in the victim’s browser. The attacker can upload a PHP file and exploit a local file inclusion (LFI) to achieve RCE.

The XSS exists because, when requesting a PHP file, the browser first renders the HTML code, and only then the JavaScript context, which allows the attacker to use HTML entities within an event handler.

The LFI, Sonar explains, exists because a user-controlled variable is concatenated to a path and not sanitized, which allows an attacker to upload a PHP file and use a path traversal via the LFI to execute the file.

Sonar reported the security defects in October 2022. One month later, the vendor patched all bugs by adding sessions and CSRF checks and restricting the installation process, by encoding the character ‘&’ for an HTML entity to prevent the XSS, and by sanitizing the user-controlled parameter to prevent the LFI.

OpenEMR version 7.0.0 resolves all vulnerabilities. Users are advised to update their installations as soon as possible.

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