CVE-2026-53909

Arbitrary File Upload in MCO

Published Jul 1, 2026 CVSS 4.0 · 5.3 Medium EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
First Time appeared Mycomplianceoffice
Mycomplianceoffice mco
Vendors & Products Mycomplianceoffice
Mycomplianceoffice mco
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
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.
Title Arbitrary File Upload in MCO
Weaknesses CWE-434
References
Metrics cvssV4_0

{'score': 5.3, 'vector': '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'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
CERT-PL
Published
Updated
Jul 1, 2026, 1:37 PM
Reserved
Jun 11, 2026, 7:44 AM
Status
Analyzed
Published
Jul 1, 2026, 1:17 PM
Modified
Oct 25, 2026, 5:10 PM