fbeta ePA3-Service-OpenSource up to 1.2.x VAU Message Construction app/vau/VAUProtokoll.py request_counter risky encryption

Summaryinfo

A vulnerability labeled as problematic has been found in fbeta ePA3-Service-OpenSource up to 1.2.x. This vulnerability affects unknown code of the file app/vau/VAUProtokoll.py of the component VAU Message Construction. Such manipulation of the argument request_counter leads to risky encryption. This vulnerability is documented as CVE-2026-50577. The attack can be executed remotely. There is not any exploit available.

Detailsinfo

A vulnerability was found in fbeta ePA3-Service-OpenSource up to 1.2.x and classified as problematic. Affected by this issue is an unknown part of the file app/vau/VAUProtokoll.py of the component VAU Message Construction. The manipulation of the argument request_counter with an unknown input leads to a risky encryption vulnerability. Using CWE to declare the problem leads to CWE-327. The product uses a broken or risky cryptographic algorithm or protocol. Impacted is confidentiality. CVE summarizes:

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.

The advisory is shared for download at github.com. This vulnerability is handled as CVE-2026-50577 since 06/04/2026. The exploitation is known to be difficult. The attack may be launched remotely. No form of authentication is required for exploitation. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1600.

Upgrading to version 1.3.0 eliminates this vulnerability.

VulDB is the best source for vulnerability data and more expert information about this specific topic.

Productinfo

Vendor

• fbeta

Name

• ePA3-Service-OpenSource

Version

• 1.0
• 1.1
• 1.2

License

• open-source

CPE 2.3info

• 🔒
• 🔒
• 🔒

CPE 2.2info

• 🔒
• 🔒
• 🔒

CVSSv4info

CVSSv3info

CVSSv2info

Exploitinginfo

Threat Intelligenceinfo

Countermeasuresinfo

Timelineinfo

Sourcesinfo

Entryinfo

VulDB is the best source for vulnerability data and more expert information about this specific topic.

Discussion