CVE-2026-44900: Epa4all client Epa4all-client Has A VAU Signature Vulnerability

HIGH
Advisory Identifier: GHSA-g8r3-5hwf-qp96
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CVSS 8.1
CWE-295
Published
Advisory Summary

CVE-2026-44900 is a HIGH (CVSS 8.1) epa4all-client has a vau signature vulnerability (CWE-295: Improper Certificate Validation) affecting Epa4all client libraries in the Maven ecosystem. The issue involves epa4all-client has a vau signature bypass. Remediation is available by upgrading affected packages to version 1.2.1.

CVE-2026-44900 at a Glance

CVE Identifier CVE-2026-44900
GHSA Identifier GHSA-g8r3-5hwf-qp96
Severity HIGH
CVSS v3.1 Base Score 8.1
CWE Classification CWE-295: Improper Certificate Validation
Affected Product Epa4all client
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 8.1

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N).

Attack Vector Adjacent (AV:A)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality High (C:H)
Integrity High (I:H)
Availability None (A:N)

How to Fix CVE-2026-44900

To remediate this vulnerability, upgrade all affected Epa4all client dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

com.oviva.telematik:epa4all-client fixed: 1.2.1 
<dependency>
    <groupId>com.oviva.telematik</groupId>
    <artifactId>epa4all-client</artifactId>
    <version>1.2.1</version>
</dependency>
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

mvn dependency:tree -Dincludes=com.oviva.telematik

How to Check if You Are Affected

To determine whether your Java application is affected by CVE-2026-44900, inspect your build dependencies using the Maven Dependency Plugin:

mvn dependency:tree -Dincludes=com.oviva.telematik

Analyze the terminal output to locate any version of Epa4all client in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.2.1), your application is affected.

Note: The mvn dependency:tree -Dincludes=com.oviva.telematik command inspects the resolved dependency graph declared in your project's POM files; it does not perform automated security scanning or inspect runtime dynamic classpaths. Always verify runtime container classpaths and shaded JARs.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-295: Improper Certificate Validation, where the product does not validate, or incorrectly validates, a certificate. In Epa4all client, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Impact In SignedPublicKeysTrustValidatorImpl.isTrusted(), the ECDSA signature verification at line 45 discards the boolean return value of Signature.verify(). The method performs certificate chain validation, OCSP check, and signature algorithm setup, but never checks whether the signature actually matches. For any structurally valid signature, it returns true. ### Patches Patched in [#34](https://github.com/oviva-ag/epa4all-client/pull/34). ### Workarounds None. ### Resources - [MS-OVIVA-EPA4ALL-d76aec](https://www.machinespirits.com/advisory/d76aec/) ### Credits [Machine Spirits](https://machinespirits.com) (contact@machinespirits.de) - Dr. rer. nat. Simon Weber - Dipl.-Inf. Volker Schönefeld - Chiara Fliegner

CVE-2026-44900 Affected Epa4all client Versions

1 component(s)
Fixed Versions:
1.2.1
Product / Package Ecosystem Affected Versions Fixed Version
com.oviva.telematik:epa4all-client
maven/com.oviva.telematik/epa4all-client
Maven
< 1.2.1
1.2.1

References

GitHub Advisory / Wiki ADVISORY
https://github.com/oviva-ag/epa4all-client/security/advisories/GHSA-g8r3-5hwf-qp96
NVD — CVE-2026-44900 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-44900
Epa4all client Source Repository REPOSITORY
https://github.com/oviva-ag/epa4all-client/pull/34
Epa4all client Source Repository REPOSITORY
https://github.com/oviva-ag/epa4all-client
www.machinespirits.com/advisory/d76aec WEB
https://www.machinespirits.com/advisory/d76aec

Frequently Asked Questions

What is CVE-2026-44900?
CVE-2026-44900 is a security vulnerability in Epa4all client involving epa4all-client has a VAU Signature bypass under CWE-295: Improper Certificate Validation.
Which Epa4all client versions are affected?
Affected versions include releases prior to 1.2.1 across affected packages: com.oviva.telematik:epa4all-client.
What version fixes CVE-2026-44900?
Upgrading to 1.2.1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is epa4all-client affected?
Yes, com.oviva.telematik:epa4all-client is affected in releases prior to 1.2.1. Upgrade your dependency to 1.2.1 or later.
What is the CVSS score of CVE-2026-44900?
CVE-2026-44900 has a CVSS v3.1 base score of 8.1 (HIGH) with vector string CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N.
What CWE is associated with CVE-2026-44900?
CVE-2026-44900 is classified under CWE-295: Improper Certificate Validation (The product does not validate, or incorrectly validates, a certificate.).
How can I check Maven dependencies for CVE-2026-44900?
Run the dependency tree command: 'mvn dependency:tree -Dincludes=com.oviva.telematik'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-g8r3-5hwf-qp96",
  "modified" : "2026-06-08T23:34:59Z",
  "published" : "2026-05-08T23:47:12Z",
  "aliases" : [ "CVE-2026-44900" ],
  "summary" : "epa4all-client has a VAU Signature bypass",
  "details" : "### Impact\nIn SignedPublicKeysTrustValidatorImpl.isTrusted(), the ECDSA signature verification at line 45 discards the boolean return value of Signature.verify(). The method performs certificate chain validation, OCSP check, and signature algorithm setup, but never checks whether the signature actually matches. For any structurally valid signature, it returns true.\n\n### Patches\nPatched in [#34](https://github.com/oviva-ag/epa4all-client/pull/34).\n\n### Workarounds\nNone.\n\n### Resources\n- [MS-OVIVA-EPA4ALL-d76aec](https://www.machinespirits.com/advisory/d76aec/)\n\n### Credits\n\n[Machine Spirits](https://machinespirits.com) (contact@machinespirits.de)\n- Dr. rer. nat. Simon Weber\n- Dipl.-Inf. Volker Schönefeld\n- Chiara Fliegner",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "com.oviva.telematik:epa4all-client"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.2.1"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 1.2.0"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/oviva-ag/epa4all-client/security/advisories/GHSA-g8r3-5hwf-qp96"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-44900"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/oviva-ag/epa4all-client/pull/34"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/oviva-ag/epa4all-client"
  }, {
    "type" : "WEB",
    "url" : "https://www.machinespirits.com/advisory/d76aec"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-295" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-08T23:47:12Z",
    "nvd_published_at" : "2026-05-26T22:16:42Z"
  }
}