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

> Attackers can bypass ECDSA signature verification in the epa4all-client library by exploiting a discarded boolean return value, allowing untrusted data to be accepted as valid.

- **Severity:** High 8.1 (`CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 26 May 2026
- **Updated:** 28 May 2026
- **Also known as:** GHSA-g8r3-5hwf-qp96

## What is CVE-2026-44900?

CVE-2026-44900 is a high-severity vulnerability in com.oviva.telematik epa4all-client, published on 26 May 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official 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.

Weakness: CWE-295 (Improper Certificate Validation)

## Which versions are affected by CVE-2026-44900?

2 open source packages ship an affected version, including com.oviva.telematik:epa4all-client.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `com.oviva.telematik:epa4all-client` | Maven | All versions | 1.2.1 |
| `com.oviva.telematik:epa4all-client` | Maven | All versions | 1.2.1 |

## How do I fix CVE-2026-44900?

Upgrade com.oviva.telematik:epa4all-client to 1.2.1 or later.

## Is CVE-2026-44900 being exploited?

There is no known exploitation of CVE-2026-44900 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-44900 and fix it if it is affected.

What it is: CVE-2026-44900 is a high-severity vulnerability in com.oviva.telematik epa4all-client, published on 26 May 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-44900 in the wild and no public exploit code.

Affected packages and fixed versions:
- com.oviva.telematik:epa4all-client (Maven): affected all versions; fixed in 1.2.1
- com.oviva.telematik:epa4all-client (Maven): affected all versions; fixed in 1.2.1

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-44900/ (Markdown: https://insights.sbomify.com/CVE-2026-44900/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-44900
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-44900
- OSV: https://osv.dev/vulnerability/CVE-2026-44900

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-44900/
Summaries are generated and may contain mistakes; the official description above is the record.