CVE-2026-53909 — Arbitrary File Upload in MCO
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-privil…
Published: 2026-07-01 · CVSS: 5.3 · CVSS 4.0
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.
Source: CVE Program · Revision 8b16575c39f1e1810c5e863010da073d2d3285e7