CVE-2026-52723: ePA 3.x Integration: VAU Server Authentication Bypass via Circular Certificate Trust
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 signedvauserverpubkeys and AUTVAUCertData 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.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
ePA 3.x Integrationto a version that resolves this vulnerability.Fixed in 1.3.0
Event History
Frequently Asked Questions
Which deployments should be treated as vulnerable?
Deployments running versions earlier than 1.3.0 are affected. The issue is fixed in version 1.3.0.
What access does an attacker need to exploit this issue?
An attacker needs a network position between the DiGA backend and the ePA system to intercept the VAU handshake. No privileges or user interaction are required.
Why does the VAU handshake accept an attacker-controlled server identity?
Affected versions disable TLS certificate verification and do not anchor the VAU certificate path and signed public keys to independent trusted material. An attacker can therefore provide controlled certificate and key material that satisfies the circular trust relationship.
What is the impact of successful exploitation?
A successful attacker can impersonate the VAU server, control negotiated session keys, and read or modify encrypted VAU traffic. This can affect Medical Information Objects handled through the authorization workflow.