CVE-2026-50577 (GCVE-0-2026-50577)
Vulnerability from cvelistv5 – Published: 2026-08-18 16:52 – Updated: 2026-08-19 14:52
VLAI
EPSS
VEX
Title
ePA 3.x Integration: AES-GCM Nonce Reuse via Frozen VAU Request Counter
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 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.
Severity
7.4 (High)
SSVC
Exploitation: none
Automatable: no
Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-19 14:52 UTC
CWE
- CWE-323 - Reusing a Nonce, Key Pair in Encryption
Assigner
References
5 references
| URL | Tags |
|---|---|
| https://github.com/fbeta-GmbH/ePA3-Service-OpenSo… | x_refsource_CONFIRM |
| https://github.com/fbeta-GmbH/ePA3-Service-OpenSo… | x_refsource_MISC |
| https://github.com/fbeta-GmbH/ePA3-Service-OpenSo… | x_refsource_MISC |
| https://github.com/fbeta-GmbH/ePA3-Service-OpenSo… | x_refsource_MISC |
| https://www.machinespirits.de/advisory/df27cd | x_refsource_MISC |
Impacted products
1 product
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| fbeta-GmbH | ePA3-Service-OpenSource |
Affected:
< 1.3.0
|
guessed |
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Browse all ATT&CK techniques and the vulnerabilities related to each.
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