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epa4all-client has a VAU Signature bypass

High severity GitHub Reviewed Published May 6, 2026 in oviva-ag/epa4all-client • Updated Jun 8, 2026

Package

maven com.oviva.telematik:epa4all-client (Maven)

Affected versions

<= 1.2.0

Patched versions

1.2.1

Description

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.

Workarounds

None.

Resources

Credits

Machine Spirits (contact@machinespirits.de)

  • Dr. rer. nat. Simon Weber
  • Dipl.-Inf. Volker Schönefeld
  • Chiara Fliegner

References

@thomasrichner-oviva thomasrichner-oviva published to oviva-ag/epa4all-client May 6, 2026
Published to the GitHub Advisory Database May 8, 2026
Reviewed May 8, 2026
Published by the National Vulnerability Database May 26, 2026
Last updated Jun 8, 2026

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Adjacent
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(2nd percentile)

Weaknesses

Improper Certificate Validation

The product does not validate, or incorrectly validates, a certificate. Learn more on MITRE.

CVE ID

CVE-2026-44900

GHSA ID

GHSA-g8r3-5hwf-qp96

Source code

Credits

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