# CVE-2026-53593: FreeScout remote code execution via incomplete upload denylist bypass

Source: https://junglewise.ai/threats/cve-2026-53593-freescout-remote-code-execution-via-incomplete-upload-denylist  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-20. Updated: 2026-07-20  
License: CC BY 4.0 with a link back

CVE-2026-53593 · Severity: high · CVSS 8.8 · Published 2026-07-20

FreeScout is an open-source help desk and shared inbox platform. A security flaw allows authenticated users to bypass file upload restrictions by using specific file extensions like .pht that were missing from the system's blocklist. An attacker can use this to upload a malicious script and execute commands on the server, potentially leading to a full system takeover, theft of customer data, and access to sensitive database credentials.

## Quick answers

**Is CVE-2026-53593 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-53593 being exploited in the wild.

**How severe is CVE-2026-53593?** High severity, with a CVSS score of 8.8, published 20 July 2026.

**Which products and versions are affected?** freescout-help-desk FreeScout < 1.8.224.

**Is there a fix for CVE-2026-53593?** 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-2026-53593 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-53593?** Check whether anything you run is named in the advisory. 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

FreeScout's file upload validation in 'Helper::$restricted_extensions' uses an incomplete denylist that fails to include the '.pht' extension (among others like .phtm and .phps). An authenticated user can send a POST request to '/uploads/upload', which saves the file with its original extension into the web-accessible 'storage/app/public/uploads/' directory. In standard Apache deployments using 'libapache2-mod-php', the default configuration executes '.pht' files as PHP scripts. This allows an attacker to upload a web shell and execute arbitrary OS commands as the 'www-data' user. This vulnerability is a bypass of the previous fix for CVE-2025-48471. The issue is resolved in version 1.8.224.

## Affected products

- freescout-help-desk FreeScout < 1.8.224

## Timeline

- 2026-06-10: advisory: GitHub Security Advisory published
- 2026-07-20: disclosed: CVE published to NVD

## References

- [https://github.com/freescout-help-desk/freescout/security/advisories/GHSA-27vp-fpg8-j8wv](https://github.com/freescout-help-desk/freescout/security/advisories/GHSA-27vp-fpg8-j8wv)