# CVE-2026-100389: GestSup remote code execution in IMAP connector attachment handling

Source: https://junglewise.ai/threats/cve-2026-100389-gestsup-versions-before-3-2-61-contain-a-remote-code-execution  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-25. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-100389 · Severity: high · CVSS 8.1 · Published 2026-09-25

GestSup is a ticket management and asset support system. An unauthenticated attacker can send emails with PHP attachments to monitored mailboxes that GestSup's IMAP connector processes; the system fails to block dangerous file extensions and stores the files in a web-accessible directory where they are executed as code when accessed. This allows complete compromise of the ticket system and potentially the underlying web server.

Technologies: [GestSup](https://junglewise.ai/threats/technologies/gestsup). Vendors: [GestSup](https://junglewise.ai/threats/vendors/gestsup).

## Quick answers

**Is CVE-2026-100389 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-100389 being exploited in the wild.

**How severe is CVE-2026-100389?** High severity, with a CVSS score of 8.1, published 25 September 2026.

**Which products and versions are affected?** GestSup before 3.2.61.

**Is there a fix for CVE-2026-100389?** 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-2026-100389 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-100389?** Check whether you run GestSup 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 IMAP connector in the core/mail.php component fails to enforce blocked file extension rules during attachment handling, allowing PHP files to pass through validation. Attachments are written directly to the web-accessible upload/ticket directory without proper sanitization. An unauthenticated attacker on the network can exploit this by sending a specially crafted email to a monitored mailbox, resulting in arbitrary code execution in the context of the web server.

## Affected products

- GestSup GestSup before 3.2.61

## Timeline

- 2026-09-25: disclosed

## References

- [https://gestsup.fr/index.php?page=changelog](https://gestsup.fr/index.php?page=changelog)
- [https://gestsup.fr/index.php?page=download](https://gestsup.fr/index.php?page=download)

## Related threats

- [GestSup stored cross-site scripting in IMAP OAuth connector](https://junglewise.ai/threats/cve-2026-102374-gestsup-versions-before-3-2-62-contain-a-stored-cross-site)
- [GestSup access control bypass in thread comment enumeration](https://junglewise.ai/threats/cve-2026-102373-gestsup-versions-before-3-2-62-fail-to-validate-ticket-ownership)
- [GestSup stored cross-site scripting in IMAP mail connector](https://junglewise.ai/threats/cve-2026-102372-gestsup-versions-before-3-2-62-fail-to-properly-sanitize-html)