CVE-2026-40566: FreeScout is a free self-hosted help desk and shared mailbox. Versions prior to 1.8.213 have a Server-Side Request Forgery (SSRF) vulnerability in the...

Description

FreeScout is a free self-hosted help desk and shared mailbox. Versions prior to 1.8.213 have a Server-Side Request Forgery (SSRF) vulnerability in the IMAP/SMTP connection test functionality of FreeScout's `MailboxesController`. Three AJAX actions `fetch_test` (line 731), `send_test` (line 682), and `imap_folders` (line 773) in `app/Http/Controllers/MailboxesController.php` pass admin-configured `in_server`/`in_port` and `out_server`/`out_port` values directly to `fsockopen()` via `Helper::checkPort()` and to IMAP/SMTP client connections with zero SSRF protection. There is no IP validation, no hostname restriction, no blocklist of internal ranges, and no call to the project's own `sanitizeRemoteUrl()` or `checkUrlIpAndHost()` functions. The validation block in `connectionIncomingSave()` is entirely commented out. An authenticated admin can configure a mailbox's IMAP or SMTP server to point at any internal host and port, then trigger a connection test. The server opens raw TCP connections (via `fsockopen()`) and protocol-level connections (via IMAP client or SMTP transport) to the attacker-specified target. The response differentiates open from closed ports, enabling internal network port scanning. When the IMAP client connects to a non-IMAP service, the target's service banner or error response is captured in the IMAP debug log and returned in the AJAX response's `log` field, making this a semi-blind SSRF that enables service fingerprinting. In cloud environments, the metadata endpoint at `169[.]254[.]169[.]254` can be probed and partial response data may be leaked through protocol error messages. This is distinct from the `sanitizeRemoteUrl()` redirect bypass (freescout-3) -- different code path, different root cause, different protocol layer. Version 1.8.213 patches the vulnerability.

Metrics

CVSS 3.1

4.1/10

CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:L/I:N/A:N

EPSS Probability

0.29%

20.8th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-918

References

Timeline

Published: Apr 21, 2026
Last Modified: Jun 17, 2026
Status: Deferred

Frequently Asked Questions

What is CVE-2026-40566?

FreeScout is a free self-hosted help desk and shared mailbox. Versions prior to 1.8.213 have a Server-Side Request Forgery (SSRF) vulnerability in the IMAP/SMTP connection test functionality of FreeScout's `MailboxesController`. Three AJAX actions `fetch_test` (line 731), `send_test` (line 682), and `imap_folders` (line 773) in `app/Http/Controllers/MailboxesController.php` pass admin-configured `in_server`/`in_port` and `out_server`/`out_port` values directly to `fsockopen()` via `Helper::checkPort()` and to IMAP/SMTP client connections with zero SSRF protection. There is no IP validation, no hostname restriction, no blocklist of internal ranges, and no call to the project's own `sanitizeRemoteUrl()` or `checkUrlIpAndHost()` functions. The validation block in `connectionIncomingSave()` is entirely commented out. An authenticated admin can configure a mailbox's IMAP or SMTP server to point at any internal host and port, then trigger a connection test. The server opens raw TCP connections (via `fsockopen()`) and protocol-level connections (via IMAP client or SMTP transport) to the attacker-specified target. The response differentiates open from closed ports, enabling internal network port scanning. When the IMAP client connects to a non-IMAP service, the target's service banner or error response is captured in the IMAP debug log and returned in the AJAX response's `log` field, making this a semi-blind SSRF that enables service fingerprinting. In cloud environments, the metadata endpoint at `169[.]254[.]169[.]254` can be probed and partial response data may be leaked through protocol error messages. This is distinct from the `sanitizeRemoteUrl()` redirect bypass (freescout-3) -- different code path, different root cause, different protocol layer. Version 1.8.213 patches the vulnerability.

How severe is CVE-2026-40566?

CVE-2026-40566 has a CVSS score of 4.1/10 (MEDIUM severity). The EPSS model estimates a 0.29% probability of exploitation in the next 30 days.

How do I fix CVE-2026-40566?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.