CVE-2026-103021 in OpenEMR
Summary
by MITRE • 11/05/2026
OpenEMR is a free and open source electronic health records and medical practice management application. From 6.0.0 until 8.3.0, interface/globals.php uses the unauthenticated authUser login parameter to populate temp_authuserid and load that account's user_settings before authentication succeeds. Existing usernames can therefore cause an additional database query and may apply visible customized settings, while nonexistent usernames skip that behavior. A remote unauthenticated actor can use timing or page differences to enumerate valid accounts for later credential attacks. This issue is fixed in version 8.3.0.
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Analysis
by VulDB Data Team • 11/05/2026
OpenEMR serves as a widely deployed open-source electronic health records and medical practice management system, handling sensitive patient data and critical clinical workflows. A significant security flaw was identified within the application's authentication flow between versions 6.0.0 and 8.3.0, specifically located in the interface/globals.php script. This vulnerability stems from a logic error where the system processes user-specific configuration settings before verifying the validity of the provided credentials. The root cause lies in the premature execution of account loading routines based on an unauthenticated input parameter named authUser. When this parameter is supplied by a remote actor, the application attempts to retrieve and apply the corresponding user's settings from the database prior to completing the authentication handshake. This architectural flaw creates a side channel that leaks information about the existence or non-existence of specific usernames within the system.
The technical mechanism of this vulnerability relies on differential analysis techniques such as timing attacks or response content comparison. When an attacker submits a username that exists in the OpenEMR database, the server performs additional database queries to fetch and apply user-specific settings, resulting in slightly longer processing times and potentially different page rendering characteristics compared to requests for non-existent users. Conversely, when a nonexistent username is provided, these specific loading routines are skipped entirely due to the absence of associated data, leading to measurably faster response times or distinct visual differences on the login interface. This discrepancy allows an unauthenticated remote actor to systematically enumerate valid usernames by observing these subtle variations in server behavior. The attacker does not need any prior access credentials and can operate from a distance, making this a low-barrier entry point for further malicious activity.
The operational impact of this vulnerability is primarily centered on information disclosure and the facilitation of subsequent attacks. By successfully enumerating valid usernames, an adversary gains valuable intelligence that significantly reduces the complexity of brute-force or credential stuffing attacks. Knowing which accounts are active allows attackers to focus their efforts on high-value targets rather than guessing randomly across a large pool of potential users. This increases the probability of successful unauthorized access and potentially leads to data breaches involving protected health information (PHI). Furthermore, if an attacker gains initial access through these enumerated credentials, they could exploit other vulnerabilities within the application to escalate privileges or exfiltrate sensitive medical records. The vulnerability is classified under CWE-204 as Observable Response Discrepancy and aligns with ATT&CK technique T1595.001, Active Scanning: Vulnerability Scanning, where adversaries probe for weaknesses in systems and networks by observing responses to various inputs.
Mitigation strategies must address both the immediate technical flaw and broader security hygiene practices. The primary remediation is to upgrade OpenEMR to version 8.3.0 or later, which corrects the authentication logic to ensure that user settings are only loaded after successful credential verification. For organizations unable to patch immediately due to operational constraints, implementing rate limiting on login endpoints can help mitigate automated enumeration attempts by throttling requests from single IP addresses. Additionally, deploying a Web Application Firewall (WAF) with rules designed to detect and block patterns associated with username enumeration attacks may provide an additional layer of defense. Security teams should also enforce strong password policies and multi-factor authentication for all user accounts to reduce the risk posed by any successfully guessed credentials. Regular security assessments and penetration testing are recommended to identify similar logic flaws in other parts of the application architecture, ensuring a robust defense-in-depth posture against information disclosure vulnerabilities.