high CVSS 8.8

CVE-2025-54366·PHP vulnerability

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.

Severity
high
Software
PHP
Fixed in
1.8.86
Published
2025-07-26

Affected versions

Until: 1.8.86

Fixed in: 1.8.86

How to fix this CVE

FreeScout users must upgrade to version 1.8.186 or later immediately to patch a critical PHP deserialization vulnerability in the conversation AJAX endpoint. Authenticated attackers with knowledge of your APP_KEY can exploit unsafe parameter handling to execute arbitrary code on your server. Apply the update through your FreeScout admin panel or by pulling the latest release from the official repository.

sudo dnf update php

Defensia detects this vulnerability

What an exploitation attempt looks like

Sample log line indicative of exploitation attempts:

POST /conversation/ajax HTTP/1.1.*attachments_all=.*[A-Za-z0-9+/]{20,}.*|POST /conversation/ajax HTTP/1.1.*attachments=.*O:[0-9]+:"[a-zA-Z_][a-zA-Z0-9_]*"

WAF mitigation (if patching is not yet possible)

Add this rule to your WAF to block exploitation attempts while you schedule the patch. 

Block or rate-limit POST requests to /conversation/ajax that contain base64-encoded payloads or PHP serialized objects in the attachments_all or attachments parameters. Additionally, restrict access to this endpoint to authenticated sessions only and require valid CSRF tokens.

How to check if you are affected

  1. Check your FreeScout version by navigating to Settings > About in the admin panel or running: grep -i 'version' /path/to/freescout/config/app.php
  2. Verify the vulnerable endpoint is accessible by testing: curl -i https://your-freescout-domain/conversation/ajax (should require authentication)
  3. Search web server logs for POST requests to /conversation/ajax with base64-encoded or serialized attachments_all or attachments parameters: grep -E 'POST.*conversation/ajax.*attachments' /var/log/apache2/access.log /var/log/nginx/access.log
  4. Confirm the patch by checking the FreeScout version displays 1.8.186 or higher in the admin panel, or run: grep -i 'version' /path/to/freescout/composer.json

FAQ

What is CVE-2025-54366?

This is a PHP object injection vulnerability in FreeScout's conversation endpoint that processes unserialized user input without validation. Authenticated attackers can instantiate arbitrary PHP objects and modify their properties to achieve remote code execution.

Is CVE-2025-54366 being actively exploited?

No, this CVE is not currently listed on the CISA Known Exploited Vulnerabilities catalog, and no public exploit code is available. However, the vulnerability is trivial to exploit for anyone with authentication credentials and the APP_KEY, so immediate patching is still critical.

What versions of FreeScout are affected by CVE-2025-54366?

All versions up to and including 1.8.185 are vulnerable. The issue is resolved in version 1.8.186 and all subsequent releases.

How do I check if my FreeScout installation is vulnerable to CVE-2025-54366?

Log into the FreeScout admin panel and navigate to Settings > About to verify your installed version. If it shows 1.8.185 or below, your system is vulnerable.

Does Defensia detect CVE-2025-54366?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If FreeScout or PHP is installed on a monitored server, CVE-2025-54366 will appear in your dashboard with remediation steps.

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References

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