Vulnerability Description
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 Score
HIGH
Related Weaknesses (CWE)
References
- https://github.com/fbeta-GmbH/ePA3-Service-OpenSource/commit/85c4c516088c38b9cf2
- 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-v
- https://www.machinespirits.de/advisory/df27cd
FAQ
What is CVE-2026-50577?
CVE-2026-50577 is a vulnerability with a CVSS score of 7.4 (HIGH). 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 unch...
How severe is CVE-2026-50577?
CVE-2026-50577 has been rated HIGH with a CVSS base score of 7.4/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-50577?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.