CVE-2025-54366: FreeScout's deserialization of untrusted data leads to Remote Code Execution

Severity: high (CVSS 8.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.1% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2025-07-26 · updated 2026-06-17
Weakness: CWE-502

Description

FreeScout is a lightweight free open source help desk and shared inbox built with PHP (Laravel framework). In versions 1.8.185 and below, there is a critical deserialization vulnerability in the /conversation/ajax endpoint that allows authenticated users with knowledge of the APP_KEY to achieve remote code execution. The vulnerability occurs when the application processes the attachments_all and attachments POST parameters through the insecure Helper::decrypt() function, which performs unsafe deserialization of user-controlled data without proper validation. This flaw enables attackers to create arbitrary objects and manipulate their properties, leading to complete compromise of the web application. This is fixed in version 1.8.186.

Affected products

freescout-help-desk freescout: before 1.8.86 — fixed in 1.8.86

How to fix

Upgrade to a fixed version: freescout-help-desk freescout 1.8.86. Check the vendor advisory for mitigations.

References

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