CVE-2026-53903 Insecure Direct Object Reference in MCO

Medium 5.3 Published 1 Jul 2026 Updated 1 Jul 2026

Attackers can access other users' trading documents by guessing IDs due to missing authorization checks in the MCO web application.

Exploited in the wild: Not known
Login needed: Any signed-in user
Attackable: Over the internet
Victim action needed: Not needed
Fix: None listed

What is CVE-2026-53903?

CVE-2026-53903 is a medium-severity missing authorization vulnerability in MyComplianceOffice MCO, published on 1 Jul 2026. Any signed-in user can exploit it over the network, with no action from the victim.

Official description

MCO is vulnerable to an Insecure Direct Object Reference (IDOR) vulnerability in the /customer/servlet/mco/webapi/trading-document/fetchPdfStatement endpoint. The application does not properly validate whether an authenticated user is authorized to access a requested document, allowing direct retrieval based on a user-supplied identifier. An attacker can access trading documents belonging to other users by providing a valid document ID. Although exploitation requires guessing the identifier, predictable ID patterns enable feasible enumeration, leading to unauthorized disclosure of sensitive information.

Because vendor contact attempts were unsuccessful, the vulnerability has only been confirmed in version 25.3.3.1 but may also affect other versions.

Weakness: CWE-639

Which versions are affected by CVE-2026-53903?

It affects 1 product.

Products include Mycomplianceoffice Mycomplianceoffice.

How do I fix CVE-2026-53903?

No fix has been published for CVE-2026-53903 yet. Limit exposure of the affected software until one is available.

Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.

Is CVE-2026-53903 being exploited?

There is no known exploitation of CVE-2026-53903 in the wild and no public exploit code.

Sources

Also known as GHSA-h63w-8j45-g3cx.