CVE-2026-103019 in OpenEMR
Summary
by MITRE • 11/05/2026
OpenEMR is a free and open source electronic health records and medical practice management application. Prior to 8.3.0, userSessionLogout() in src/RestControllers/AuthorizationController.php uses decodeToken() to process an id_token_hint without verifying its signature and, when the referenced trusted session is absent, redirects to the caller-supplied post_logout_redirect_uri before validating it against the client's registered redirect URIs. An unauthenticated attacker can craft a logout link that sends a user to an arbitrary external site and invalidates the user's session, enabling convincing phishing flows from the legitimate logout endpoint. The endpoint is reachable when the OpenEMR REST API is enabled. 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. Within this ecosystem, the integrity of authentication mechanisms and session management processes is paramount to maintaining confidentiality and trust. A significant security flaw was identified in versions prior to 8.3.0 within the REST API implementation, specifically affecting the userSessionLogout function located in src/RestControllers/AuthorizationController.php. This vulnerability stems from improper handling of OpenID Connect parameters during the logout process, creating a pathway for unauthenticated attackers to manipulate session states and redirect users maliciously.
The technical core of this vulnerability lies in two distinct failures within the authorization controller logic. First, when processing an id_token_hint parameter, the application invokes decodeToken() but fails to verify the cryptographic signature of the token. In standard OpenID Connect implementations, tokens must be validated against a trusted issuer and signed by a recognized authority to ensure their authenticity. By skipping this verification step, the system accepts any malformed or attacker-controlled token as valid input for session termination logic. Second, upon determining that the referenced trusted session is absent, the application proceeds to redirect the user to a post_logout_redirect_uri provided in the request without validating it against the client's registered redirect URIs list. This omission violates fundamental security principles regarding destination validation during authentication flows.
The operational impact of these flaws allows an unauthenticated attacker to execute a sophisticated phishing attack with high credibility. By crafting a malicious logout link that includes a forged id_token_hint and a controlled post_logout_redirect_uri, the attacker can trigger the session invalidation process for any targeted user who clicks the link. Once clicked, the victim's active OpenEMR session is terminated, creating a sense of urgency or confusion. The application then redirects the victim to an arbitrary external site specified by the attacker rather than a legitimate internal page. This sequence effectively mimics a standard logout procedure from the user perspective but results in redirection to a phishing domain designed to steal credentials or deliver malware. Because the attack leverages the legitimate OpenEMR interface and endpoint, it bypasses many visual trust indicators that users rely on to identify safe websites.
This vulnerability is classified under CWE-20 as Improper Input Validation, specifically regarding the failure to validate inputs against expected formats and security constraints such as signature verification and allowed destination lists. It also aligns with ATT&CK technique T1566.002, which covers Spearphishing Links, where attackers use links that appear legitimate but lead to malicious destinations. The risk is particularly acute in healthcare environments where trust in the application interface is high, making users less likely to suspect foul play when redirected from a familiar domain like OpenEMR.
To mitigate this vulnerability, organizations running versions of OpenEMR prior to 8.3.0 must upgrade immediately to version 8.3.0 or later, which addresses these logic flaws by implementing proper signature verification for id_token_hint and enforcing strict validation of the post_logout_redirect_uri against registered client URIs. Until an upgrade is performed, administrators should consider disabling the REST API if it is not strictly required for operational workflows, thereby removing the attack surface entirely. Additionally, monitoring logs for unusual logout requests containing malformed tokens or unexpected redirect destinations can help in detecting attempted exploitation activities.