CVE-2026-53593 freescout vulnerability
FreeScout is a free help desk and shared inbox built with PHP's Laravel framework. Prior to version 1.8.224, the denylist that neutralizes dangerous file uploads (`Helper::$restricted_extensions`) is incomplete: it does not cover the `.pht` extension. The authenticated upload endpoint `POST /uploads/upload` (`SecureController@upload`) stores files with their original extension into the web-accessible directory `storage/app/public/uploads/` (served at `/storage/uploads/`). On the standard Apache + `libapache2-mod-php` deployment, the default handler `<FilesMatch ".+\.ph(ar|p[3457]?|t|tml)$">` executes `.pht`, so **any authenticated agent can upload a `.pht` web shell and run arbitrary commands as the web-server user** (`www-data`). This is a direct bypass of the fix for CVE-2025-48471, which added `phtml`/`phar` but not `pht` (nor `phtm`, `phps`). Version 1.8.224 contains an updated fix.
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freescout-help-desk freescout should be reviewed and updated if it matches the affected versions. The recommended fix is to apply the vendor-supported patched version or the mitigation steps below, then retest the public website with Fixnx.
Who is affected
Affected versions
- < 1.8.224
Fixed versions
- Apply the latest vendor-supported patched version.
How to fix it
CVE-2026-53593 affects freescout and involves code or command execution. Successful exploitation may let an attacker run unintended code or operating-system commands in the affected process. Prioritize internet-facing, privileged, automation, and production deployments. Upgrade freescout to 1.8.224 or a later vendor-supported fixed release.
- Inventory every deployment, device, package, plugin, container, build, and environment that uses freescout.
- Compare the installed version with the recorded affected range: < 1.8.224.
- Upgrade freescout to 1.8.224 or a later vendor-supported fixed release.
- Until patched, disable the affected feature, limit untrusted input, and run the service with the lowest practical privileges.
- Review configuration, roles, tokens, network paths, and exposed endpoints connected to freescout; remove access that is not required.
- Review process, shell, web, audit, and network logs for unexpected commands, child processes, downloads, callbacks, or changed files.
- If exploitation is suspected, isolate affected assets, preserve evidence, rotate exposed credentials or keys, restore trusted data, and rebuild compromised systems before returning them to service.
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Verify the fix
- Confirm every affected asset now runs the fixed vendor-supported release or has the documented mitigation for CVE-2026-53593 in place.
- Use a safe regression test to confirm the affected code or command execution path no longer produces the vulnerable behavior.
- Confirm temporary access controls, endpoint restrictions, network blocks, and least-privilege settings remain effective after the update.
- Review post-remediation logs and rerun Fixnx plus the relevant package, dependency, firmware, browser, or product-specific security check.
- Document affected assets, versions, changes, validation evidence, reviewed logs, and any credential rotation, cleanup, or replacement completed.
Related categories
Related security risks
More published guidance from the same primary category.
Trusted references
FAQ
What is affected by CVE-2026-53593?
freescout-help-desk freescout versions listed as affected should be reviewed: < 1.8.224.
What should I fix first?
Start with internet-facing sites, admin panels, login flows, plugins, themes, modules, packages, and systems that process user-controlled input or sensitive data.
How do I confirm the fix worked?
Apply the patched version or mitigation, clear caches where relevant, retest the affected workflow, and run a new Fixnx scan to verify public website exposure signals.
How are Fixnx security risk categories chosen?
Fixnx keeps one canonical risk page and assigns only broad, relevant categories such as ecosystem, technology area, or vulnerability class.