---
id: CVE-2026-50577
title: >-
  ePA 3.x Integration implements the authorization workflow and writes Medical
  Information Objects to Germany's electronic patient record
summary: >-
  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 leaves request_counter unchanged in
  app/vau/VAUProtokoll.py whil…
severity: high
cvss: 7.4
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N'
cwe:
  - CWE-323
published: '2026-08-18'
updated: '2026-09-08'
sourceUpdated: '2026-09-08T21:02:26.047'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-50577'
references:
  - url: >-
      https://github.com/fbeta-GmbH/ePA3-Service-OpenSource/commit/85c4c516088c38b9cf2343f388ad67a6744e9814
    label: security-advisories@github.com
  - url: 'https://github.com/fbeta-GmbH/ePA3-Service-OpenSource/pull/10'
    label: security-advisories@github.com
  - url: 'https://github.com/fbeta-GmbH/ePA3-Service-OpenSource/releases/tag/1.3.0'
    label: security-advisories@github.com
  - url: >-
      https://github.com/fbeta-GmbH/ePA3-Service-OpenSource/security/advisories/GHSA-vmfm-3f7g-r9qg
    label: security-advisories@github.com
  - url: 'https://www.machinespirits.de/advisory/df27cd'
    label: security-advisories@github.com
tags:
  - nvd
epss: 0.00513
epssPercentile: 0.41183
ingestedAt: '2026-09-08T21:11:12.282Z'
---

## Overview

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 leaves request_counter unchanged in app/vau/VAUProtokoll.py while constructing VAU messages. The frozen client request counter causes the server side to reuse AES-GCM nonce and key combinations across responses. A network attacker who collects repeated ciphertexts can recover the XOR of plaintexts and use predictable inner HTTP headers and JSON fields to recover sensitive data, including patient health records. Repeated nonces can also enable recovery of the GHASH authentication key through the Joux forbidden attack, allowing forged AES-GCM messages and injection of malicious responses. The response-counter check also fails to maintain last_response_counter, weakening replay and ordering validation. This issue is fixed in version 1.3.0.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.