Meona Client: Improper Access Control
CVE-2026-0856 is a high-severity improper access control vulnerability in Meona Client from Mesalvo, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. Affected Meona Client versions: 2024.10; 2025.04; 2026.03. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.13% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Check which version of Meona Client you run against the affected versions below, and install the vendor's latest release.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Mesalvo | Meona Client | 2024.10; 2025.04; 2026.03 | Not stated |
| Mesalvo | Meona Server | 2024.10; 2025.04; 2026.03 | Not stated |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by CNA.
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.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Access Control
The product does not restrict or incorrectly restricts access to a resource from an unauthorized actor.
How developers prevent this class of flaw
- Very carefully manage the setting, management, and handling of privileges. Explicitly manage trust zones in the software.
- Compartmentalize the system to have safe areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area. Ensure that appropriate compartmentalization is built into the system design, and the compartmentalization allows for and reinforces privilege separation functionality. Architects and designers should rely on the principle of least privilege to decide the appropriate time to use privileges and the time to drop privileges.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Other references
Recent Improper Access Control vulnerabilities
- 8.6 High severity
- 8.1 High severity
- 7.3 High severity
- 8.1 High severity
- 7.1 High severity
- 9.9 Critical severity
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