CVE-2026-53909
Arbitrary File Upload in MCO
- State
- Published
- Severity
- 5.3 Medium
- Published
- Jul 1, 2026
- Updated
- Jul 1, 2026
- Reserved
- Jun 11, 2026
Description
MCO does not correctly validate types of uploaded files. File upload validation functionality relies only on client-side checks, which can be bypassed. An authorized, low-privileged attacker can upload files with arbitrary types to the server.
Because vendor contact attempts were unsuccessful, the vulnerability has only been confirmed in version 25.3.3.1 but may also affect other versions.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 5.3 Medium | CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N | CERT-PL |
Weaknesses
- CWE-434 Unrestricted Upload of File with Dangerous Type
Affected Products
| Product | Versions |
|---|---|
MCOMyComplianceOffice |
|
References
- https://cert.pl/en/posts/2026/07/CVE-2026-53902third-party-advisory
- https://mco.mycomplianceoffice.com/product
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