# CVE-2026-0856: Missing authorization in Meona Client

> Authenticated users can escalate privileges to administrator by modifying client binaries, requiring network access within closed hospital networks.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 20 May 2026
- **Updated:** 25 Sep 2026
- **Also known as:** GHSA-q549-3jgw-crc8

## What is CVE-2026-0856?

CVE-2026-0856 is a high-severity missing authorization vulnerability in Mesalvo Meona Client, published on 20 May 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

Improper Access Control vulnerability in Mesalvo MEONA (MEONA Client and MEONA Server) allows an authenticated MEONA user to access administrative functions of the MEONA Client (admin panel). The MEONA Server does not independently verify the role asserted by the MEONA Client. A user who holds a valid MEONA user account and is able to execute a modified copy of the MEONA Client on a device within the operating hospital's network can assert an administrator role and access administrative functions with regular user credentials.
Exploitation requires: (1) a valid MEONA user account issued by the operating hospital; (2) network access to the MEONA Server, which is operated exclusively within closed hospital networks without exposure to the public Internet (where a hospital permits remote access to that network at all, it is only through the hospital's own remote-access infrastructure (e.g. VPN) under the hospital's control); (3) the ability to modify MEONA Client binaries and to execute the modified copy on a device in that network. On managed devices with application control, as recommended in Mesalvo's hardening guidance (MSA-2026-001), this requires local administrator privileges on the device. Mesalvo is not aware of any exploitation outside the reported security test.
This issue affects MEONA Client and MEONA Server in versions 2024.10, 2025.04 and 2026.03. Mitigations are available with MEONA 2025.04.24 and 2026.03.02 (planned Q4 2026); see Mesalvo Security Advisory MSA-2026-001.

Weakness: CWE-284 (Improper Access Control)

## Which versions are affected by CVE-2026-0856?


## How do I fix CVE-2026-0856?

No fix has been published for CVE-2026-0856 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-0856 being exploited?

There is no known exploitation of CVE-2026-0856 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-0856 and fix it if it is affected.

What it is: CVE-2026-0856 is a high-severity missing authorization vulnerability in Mesalvo Meona Client, published on 20 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-2026-0856 in the wild and no public exploit code.

Affected product: Mesalvo Meona Client. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2026-0856/ (Markdown: https://insights.sbomify.com/CVE-2026-0856/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-0856
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-0856
- OSV: https://osv.dev/vulnerability/CVE-2026-0856

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-0856/
Summaries are generated and may contain mistakes; the official description above is the record.