Quick answers
- Is CVE-2026-53909 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-53909 being exploited in the wild.
- How severe is CVE-2026-53909?
- Informational severity, with a CVSS score of 5.3, published 1 July 2026.
- Which products and versions are affected?
- MyComplianceOffice MCO 25.3.3.1.
- Is there a fix for CVE-2026-53909?
- No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
- How is CVE-2026-53909 attacked?
- It is attacked over the network, in a network appliance.
- Am I affected by CVE-2026-53909?
- Check whether you run MyComplianceOffice MCO at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
The vulnerability is classified as Unrestricted Upload of File with Dangerous Type (CWE-434). The root cause is that the MCO application performs file type validation only on the client side (e.g., via JavaScript or HTML attributes), which can be easily intercepted and bypassed using a proxy or custom request. An authenticated attacker with low privileges can exploit this to upload files with arbitrary extensions or MIME types to the server. While the impact on confidentiality and availability is rated as none by the reporter, it poses a risk to system integrity. The vulnerability was confirmed in version 25.3.3.1, and no patch has been confirmed due to unsuccessful vendor contact.
Affected products
- MyComplianceOffice MCO 25.3.3.1
Timeline
- 2026-07-01: disclosed: Vulnerability disclosed by CERT Polska
- 2026-07-01: advisory: CVE-2026-53909 published