CVE-2026-50577
ePA 3.x Integration: AES-GCM Nonce Reuse via Frozen VAU Request Counter
- Published
- Updated
- Reserved
- Assigned by
- GitHub_M
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.
Timeline
ID reserved
By GitHub_M
- 3 months later
· 3 months later
Published
- 1 day later
· 1 day later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_MCNA (assigner) | 3.1 | High7.4 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N |
| NVDNVD · Deferred | 3.1 | High7.4 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N |
- EPSS (exploitation in 30 days)
- 0.51% · top 56% of all CVEs (7 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: no · Technical impact: total
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.4.
Weakness
Affected products
fbeta-GmbH · ePA3-Service-OpenSource
- affected < 1.3.0
References (5)
- https://github.com/fbeta-GmbH/ePA3-Service-OpenSource/security/advisories/GHSA-vmfm-3f7g-r9qg (opens in a new tab)x_refsource_CONFIRM
- https://github.com/fbeta-GmbH/ePA3-Service-OpenSource/pull/10 (opens in a new tab)x_refsource_MISC
- https://github.com/fbeta-GmbH/ePA3-Service-OpenSource/commit/85c4c516088c38b9cf2343f388ad67a6744e9814 (opens in a new tab)x_refsource_MISC
- https://github.com/fbeta-GmbH/ePA3-Service-OpenSource/releases/tag/1.3.0 (opens in a new tab)x_refsource_MISC
- https://www.machinespirits.de/advisory/df27cd (opens in a new tab)x_refsource_MISC
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://trackcve.app/cve/CVE-2026-50577)Record last updated .