CVE-2026-50577

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.

CVSS v3 7.4 HIGH

7.4^/10

CVSS v3 : HIGH

Vector :

Exploitability : 2.2 / Impact : 5.2

Attack Vector NETWORK

Attack Complexity HIGH

Privileges Required NONE

User Interaction NONE

Confidentiality Impact HIGH

Integrity Impact HIGH

Availability Impact NONE

Scope UNCHANGED

References

Link	Resource
https://github.com/fbeta-GmbH/ePA3-Service-OpenSource/commit/85c4c516088c38b9cf2343f388ad67a6744e9814
https://github.com/fbeta-GmbH/ePA3-Service-OpenSource/pull/10
https://github.com/fbeta-GmbH/ePA3-Service-OpenSource/releases/tag/1.3.0
https://github.com/fbeta-GmbH/ePA3-Service-OpenSource/security/advisories/GHSA-vmfm-3f7g-r9qg
https://www.machinespirits.de/advisory/df27cd

Configurations

No configuration.

History

No history.

Information

Published : 2026-08-18 17:16

Updated : 2026-09-08 21:02

NVD link : CVE-2026-50577

Mitre link : CVE-2026-50577

CVE.ORG link : CVE-2026-50577

JSON object : View

Products Affected

No product.

CWE

CWE-323

Reusing a Nonce, Key Pair in Encryption

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