CVE-2026-53909Network attack vector

Authenticated arbitrary file upload via client-side validation

Published Jul 1, 2026 · Updated Jul 1, 2026

Unrestricted file upload in MyComplianceOffice MCO 25.3.3.1 allows remote authenticated users to store arbitrary file types on the server. The upload workflow enforces file-type restrictions only in client-side checks and performs no equivalent server-side type validation. Low-privileged credentials are sufficient; the established impact is unauthorized file storage, with no published evidence that uploaded files execute.

CVSS severity5.3
Medium
EPSS probability0.39%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Unrestricted file upload in MyComplianceOffice MCO 25.3.3.1 allows remote authenticated users to store arbitrary file types on the server. The upload workflow enforces file-type restrictions only in client-side checks and performs no equivalent server-side type validation. Low-privileged credentials are sufficient; the established impact is unauthorized file storage, with no published evidence that uploaded files execute.

The record

CVE
CVE-2026-53909
Published
Jul 1, 2026
Updated
Jul 1, 2026
Vendor
MyComplianceOffice
Product
MCO
Classifications
CWE-434, T1105
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jul 1, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 1, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=25.3.3.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

MyComplianceOffice · MCOversion=25.3.3.1

Published CVSS scores

6.5NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
5.3CERT.PLCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-434Unrestricted Upload of File with Dangerous Type
T1105Ingress Tool Transfer

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo