CVE-2026-53909 — MEDIUM (6.5)

Vulnerability 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.

CVSS Score

6.5

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N

Attack Vector

NETWORK

Attack Complexity

LOW

Privileges Required

LOW

User Interaction

NONE

Scope

UNCHANGED

Confidentiality

NONE

Integrity

HIGH

Availability

NONE

Affected Products

Vendor	Product	Versions
Mycomplianceoffice	Mycomplianceoffice	25.3.3.1

Related Weaknesses (CWE)

CWE-434

References

https://cert.pl/en/posts/2026/07/CVE-2026-53902Third Party Advisory
https://mco.mycomplianceoffice.com/Product

FAQ

What is CVE-2026-53909?

CVE-2026-53909 is a vulnerability with a CVSS score of 6.5 (MEDIUM). 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 uploa...

How severe is CVE-2026-53909?

CVE-2026-53909 has been rated MEDIUM with a CVSS base score of 6.5/10. Review the CVSS metrics above for detailed severity breakdown.

Is there a patch for CVE-2026-53909?

Check the references section above for vendor advisories and patch information. Affected products include: Mycomplianceoffice Mycomplianceoffice.