CVE-2026-53909
File upload validation functionality relies only on client-side checks, which can be bypassed.
Does this matter?
Lower severity and a low EPSS score (0.39%). Track it; it rarely justifies an emergency change on its own.
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 4.0
- 5.3 MEDIUMCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/M
- EPSS
- 0.39% probability · 33th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-434
- Affected
- mycomplianceoffice/mycomplianceoffice
- Source
- cvd@cert.pl
EPSS 0.4% since 27 October 2026; no change recorded yet. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
References
- https://cert.pl/en/posts/2026/07/CVE-2026-53902Third Party Advisory
- https://mco.mycomplianceoffice.com/Product
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.