CVE-2026-0856

Summary

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.

Affected Software

VendorProductVersion RangeStatus
MesalvoMeona Client2024.10affected
MesalvoMeona Client2025.04affected
MesalvoMeona Client2026.03affected
MesalvoMeona Server2024.10affected
MesalvoMeona Server2025.04affected
MesalvoMeona Server2026.03affected

Weaknesses

  • CWE-284: CWE-284: Improper Access Control

Workarounds

MEONA 2025.04.24 and 2026.03.02 (Q4 2026) introduce code signing of all MEONA Client executables and assemblies and integrity verification of the client assemblies at start-up. Operators should enforce application control on MEONA workstations so that only Mesalvo-signed binaries execute, withhold local administrator rights from clinical users, provision MEONA users through the hospital's central identity and access management, and keep the MEONA network zone segmented without Internet exposure. Details: Mesalvo Security Advisory MSA-2026-001.

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: none
    • Automatable: no
    • Technical Impact: total

References