Vulnerability · Published Jul 1, 2026 · Assigned by CERT-PL

CVE-2026-53909Arbitrary File Upload in MCO

Medium 5.3

In plain English

A medium-severity unrestricted file upload in MCO from MyComplianceOffice. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 34% of all known vulnerabilities).

Severity (CVSS 4.0)5.3Medium

Exploit odds (30 days)0.4%top 66.2% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official 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.

Affected products (as reported)

Vendor	Product	Versions
MyComplianceOffice	MCO	25.3.3.1

Weakness: CWE-434 · 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

References

https://cert.pl/en/posts/2026/07/CVE-2026-53902 third-party-advisory
https://mco.mycomplianceoffice.com/ product