CVE-2026-24890: OpenEMR Auth Bypass Vulnerability

CVE-2026-24890 Overview

OpenEMR is a free and open source electronic health records and medical practice management application. Prior to version 8.0.0, an authorization bypass vulnerability exists in the patient portal signature endpoint that allows authenticated portal users to upload and overwrite provider signatures by setting type=admin-signature and specifying any provider user ID. This critical flaw enables signature forgery on medical documents, potentially leading to legal compliance violations and fraud within healthcare environments.

Critical Impact

Authenticated patient portal users can forge provider signatures on medical documents, potentially enabling fraudulent prescriptions, falsified medical records, and significant legal and regulatory violations in healthcare environments.

Affected Products

• OpenEMR versions prior to 8.0.0
• OpenEMR Patient Portal signature functionality
• Healthcare facilities using OpenEMR for electronic health records management

Discovery Timeline

• 2026-02-25 - CVE-2026-24890 published to NVD
• 2026-02-26 - Last updated in NVD database

Technical Details for CVE-2026-24890

Vulnerability Analysis

This authorization bypass vulnerability (CWE-285) affects the patient portal signature endpoint in OpenEMR. The flaw allows authenticated portal users to exceed their intended privileges by manipulating request parameters to upload and overwrite provider signatures. By setting the type parameter to admin-signature and specifying an arbitrary provider user ID, a malicious patient portal user can effectively forge signatures belonging to healthcare providers.

The vulnerability is particularly severe in healthcare environments where digital signatures on medical documents carry legal weight. Forged signatures could be used to authorize prescriptions, falsify treatment records, or manipulate consent forms, all of which have serious implications for patient safety and regulatory compliance under frameworks like HIPAA.

Root Cause

The root cause of this vulnerability is improper authorization checking in the signature saving functionality. The application fails to verify that the authenticated user has the necessary privileges to modify signatures of the specified type and user ID. When processing signature upload requests, the endpoint accepts user-controlled parameters (type and user ID) without validating that the requesting user is authorized to perform operations on those resources.

Attack Vector

The attack can be executed over the network by any authenticated patient portal user. The attacker crafts a malicious request to the signature endpoint (portal/sign/lib/save-signature.php) with the following manipulated parameters:

1. Set type=admin-signature to target provider-level signatures
2. Specify any provider user ID as the target
3. Upload a new signature image to overwrite the legitimate provider signature

This allows horizontal and vertical privilege escalation, enabling a low-privileged patient user to modify resources belonging to higher-privileged provider accounts.

  * @link      http://www.open-emr.org
  * @author    Jerry Padgett <sjpadgett@gmail.com>
  * @author    Brady Miller <brady.g.miller@gmail.com>
+ * @author    Michael A. Smith <michael@opencoreemr.com>
  * @copyright Copyright (c) 2016-2021 Jerry Padgett <sjpadgett@gmail.com>
  * @copyright Copyright (c) 2019 Brady Miller <brady.g.miller@gmail.com>
+ * @copyright Copyright (c) 2026 OpenCoreEMR Inc <https://opencoreemr.com/>
  * @license   https://github.com/openemr/openemr/blob/master/LICENSE GNU General Public License 3
  */

Source: GitHub Commit Reference

The patch adds proper authorization validation to ensure only authorized users can modify provider signatures.

Detection Methods for CVE-2026-24890

Indicators of Compromise

• Unexpected signature file modifications in the OpenEMR signature storage directories
• Web server logs showing requests to portal/sign/lib/save-signature.php with type=admin-signature from patient portal sessions
• Audit logs indicating provider signatures modified by non-provider accounts
• Medical documents with signatures that providers deny authorizing

Detection Strategies

• Monitor web application logs for requests to the signature endpoint containing suspicious parameter combinations such as type=admin-signature from patient-level accounts
• Implement file integrity monitoring on signature storage directories to detect unauthorized modifications
• Configure application-level logging to track signature creation and modification events with associated user context
• Deploy web application firewall rules to flag parameter manipulation attempts targeting signature endpoints

Monitoring Recommendations

• Enable comprehensive audit logging within OpenEMR to track all signature-related operations
• Implement real-time alerting for signature modifications that do not match expected user role permissions
• Review OpenEMR access logs regularly for anomalous patterns in signature endpoint access
• Configure SIEM rules to correlate patient portal authentication events with provider signature modifications

How to Mitigate CVE-2026-24890

Immediate Actions Required

• Upgrade OpenEMR to version 8.0.0 or later immediately
• Review signature audit logs for evidence of exploitation prior to patching
• Verify integrity of existing provider signatures in the system
• Temporarily restrict patient portal access if immediate patching is not possible

Patch Information

OpenEMR version 8.0.0 addresses this vulnerability by implementing proper authorization checks in the signature endpoint. The fix ensures that only authorized users can modify signatures matching their permission level. The security patch is available via the GitHub commit a29c0f7ac0975429a85cd09a3ff12ee0dcdb4478. Additional details are available in the GitHub Security Advisory GHSA-xc8x-mfh8-9xvh.

Workarounds

• Implement web application firewall rules to block requests to portal/sign/lib/save-signature.php containing type=admin-signature parameter from patient portal sessions
• Disable patient portal signature functionality temporarily until the patch can be applied
• Implement network segmentation to restrict patient portal access to signature management endpoints
• Enable enhanced logging and monitoring to detect exploitation attempts while awaiting patching

# Example Apache ModSecurity rule to block exploitation attempts
SecRule REQUEST_URI "@contains /portal/sign/lib/save-signature.php" \
  "id:1001,phase:2,deny,status:403,chain,msg:'CVE-2026-24890 Exploitation Attempt'"
SecRule ARGS:type "@streq admin-signature" ""