CVE-2026-52723 in ePA3-Service-OpenSource
Summary
by MITRE • 08/18/2026
ePA 3.x Integration implements the authorization workflow and writes Medical Information Objects to Germany's electronic patient record. Prior to 1.3.0, ePA 3.x Integration performs VAU server certificate validation in app/vau/VAUProtokoll.py without anchoring the signed_vau_server_pub_keys and AUT_VAU_CertData certificate path to independent trusted material. A network-positioned attacker between the DiGA backend and the ePA system can intercept the VAU handshake, supply attacker-controlled certificate and key material, and satisfy the circular trust relationship. Because TLS certificate verification is also disabled in affected versions, no independent server-authentication layer prevents the attack. The attacker can impersonate the VAU server, control the negotiated session keys, and read or modify all encrypted VAU traffic. This issue is fixed in version 1.3.0.
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Analysis
by VulDB Data Team • 08/18/2026
The ePA 3.x Integration component serves as a critical bridge for implementing authorization workflows and writing Medical Information Objects to Germany's electronic patient record system. In versions prior to 1.3.0, this integration contains a severe cryptographic implementation flaw within the Virtual Access Unit server authentication process. The vulnerability stems from improper validation of TLS certificates during the VAU handshake sequence located in the app/vau/VAUProtokoll.py module. Specifically, the application fails to anchor the signed_vau_server_pub_keys and AUT_VAU_CertData certificate paths to independent trusted material such as a recognized Certificate Authority or a pre-configured trust store. This lack of anchoring creates a circular trust relationship where the client accepts any presented certificate without verifying its origin against a known root of trust, effectively nullifying the security guarantees provided by public key infrastructure mechanisms.
This architectural deficiency allows for sophisticated man-in-the-middle attacks when an adversary is positioned between the DiGA backend and the ePA system. Because TLS certificate verification is also disabled in these affected versions, there is no independent server-authentication layer to prevent impersonation attempts. An attacker can intercept the VAU handshake process and supply their own controlled certificate and key material that satisfies the flawed validation logic. By successfully completing this handshake with self-signed or attacker-controlled credentials, the adversary establishes a legitimate-looking encrypted session with both parties involved in the communication flow. This capability enables the attacker to fully impersonate the VAU server without triggering any security alerts or connection failures within the application layer.
The operational impact of this vulnerability is severe due to the sensitive nature of healthcare data handled by the ePA system. Once the man-in-the-middle position is established, the attacker gains complete control over the negotiated session keys used for encrypting communications between the client and server. This allows the adversary to decrypt all VAU traffic in real-time, exposing protected health information including patient diagnoses, medication records, and personal identifiers. Furthermore, the ability to modify encrypted traffic means an attacker can alter medical data being written to the electronic patient record without detection. Such tampering could lead to incorrect treatments, compromised patient safety, and significant violations of data integrity requirements mandated by healthcare regulations like HIPAA or GDPR depending on the jurisdictional context.
From a classification perspective, this vulnerability aligns with CWE-295 Improper Certificate Validation as it involves failing to properly validate certificates against trusted authorities. It also maps to MITRE ATT&CK technique T1078 Valid Accounts and potentially T1041 Exfiltration Over C2 Channel if the intercepted data is exfiltrated, though primarily it represents a failure in authentication mechanisms that enables subsequent interception activities classified under T1557 Adversary-in-the-Middle. The root cause lies in the application's reliance on self-signed or unanchored certificates rather than enforcing strict certificate chain validation against a trusted root store.
To mitigate this vulnerability, organizations must upgrade to version 1.3.0 of ePA 3.x Integration where these cryptographic controls have been corrected. Until an upgrade is feasible, it is imperative to ensure that the VAU server presents certificates signed by a recognized Certificate Authority and that clients are configured to validate certificate chains against trusted roots rather than accepting any presented key material. Network-level protections such as mutual TLS with strict client-side verification can also provide additional layers of defense. Regular security audits should verify that no application code disables standard TLS validation features, ensuring that all cryptographic handshakes adhere to industry best practices for secure communication channels in healthcare environments.