What is CVE-2026-100389?

CVE-2026-100389 is a high-severity vulnerability in Gestsup, classified under Unrestricted Upload of File with Dangerous Type. CVSS score: 8.1/10. Published 2026-09-25.

How severe is CVE-2026-100389?

High severity. CVSS v3 base score is 8.1 out of 10.

Arbitrary file upload in Gestsup

CVE-2026-100389

GestSup versions before 3.2.61 contain a remote code execution vulnerability in the basic IMAP connector's attachment handling that fails to skip blocked file extensions. Unauthenticated attackers can send emails with PHP attachments to monitored mailboxes, which are written to the web-accessible upload/ticket directory and executed when accessed.

Vulnerability class: Unrestricted File Upload

Published 2026-09-25.

CVSS v3 metric

CVSS v3 base score 8.1 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.

Affected products

Gestsup

Weakness classification (CWE)

CWE-434 — Unrestricted Upload of File with Dangerous Type

References

gestsup.fr/index.php (release-notes)
gestsup.fr/index.php (product)
www.vulncheck.com/advisories/gestsup-before-3.2.61-remote-code-execution-via-im… (third-party-advisory)

Frequently asked questions

What is CVE-2026-100389?: CVE-2026-100389 is a high-severity vulnerability in Gestsup, classified under Unrestricted Upload of File with Dangerous Type. CVSS score: 8.1/10. Published 2026-09-25.
How severe is CVE-2026-100389?: High severity. CVSS v3 base score is 8.1 out of 10.