Auth bypass in Mycomplianceoffice Mco
CVE-2026-53902
MCO does not properly enforce authorization checks in the /customer/servlet/mco/webapi/profile-sections/group-membership endpoint. An authenticated user can modify their group membership without proper authorization checks, allowing privilege escalation. An attacker can add themselves to arbitrary groups by supplying a valid group ID, which can be obtained via other application functionalities (e.g. /customer/servlet/mco/webapi/group/picker/groups), provided he has necessary permissions, or potentially inferred through brute-force techniques. Because vendor contact attempts were unsuccessful, the vulnerability has only been confirmed in version 25.3.3.1 but may also affect other versions.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N.
EPSS exploit prediction
EPSS: 0.003 (25.3th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 25th percentile — 25.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: 0.000
Affected products
- Mycomplianceoffice Mco — versions 25.3.3.1
- Mycomplianceoffice — versions 25.3.3.1
Weakness classification (CWE)
References
- cert.pl/en/posts/2026/07/CVE-2026-53902 (Third Party Advisory, third-party-advisory)
- mco.mycomplianceoffice.com/ (Product, product)
Frequently asked questions
- What is CVE-2026-53902?
- CVE-2026-53902 is a medium-severity vulnerability in Mycomplianceoffice Mco, classified under Incorrect Privilege Assignment. CVSS score: 6.5/10. Published 2026-07-01.
- How severe is CVE-2026-53902?
- Medium severity. CVSS v3 base score is 6.5 out of 10.