CVE-2026-50577 ePA 3.x Integration: AES-GCM Nonce Reuse via Frozen VAU Request Counter
A network attacker can recover sensitive patient health records and forge messages due to AES-GCM nonce reuse in the ePA 3.x Integration library.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-50577?
CVE-2026-50577 is a high-severity vulnerability in fbeta-GmbH ePA3-Service-OpenSource, published on 18 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-323
Which versions are affected by CVE-2026-50577?
How do I fix CVE-2026-50577?
No fix has been published for CVE-2026-50577 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-50577 being exploited?
There is no known exploitation of CVE-2026-50577 in the wild and no public exploit code.
Sources
Also known as GHSA-vmfm-3f7g-r9qg.