CVE-2026-40497
FreeScout Vulnerable to CSS Injection via Stored Style Tag in Mailbox Signature (CSRF Token Exfiltration)
Description
FreeScout is a free self-hosted help desk and shared mailbox. Prior to version 1.8.213, FreeScout's `Helper::stripDangerousTags()` removes `<script>`, `<form>`, `<iframe>`, `<object>` but does NOT strip `<style>` tags. The mailbox signature field is saved via POST /mailbox/settings/{id} and later rendered unescaped via `{!! $conversation->getSignatureProcessed([], true) !!}` in conversation views. CSP allows `style-src * 'self' 'unsafe-inline'`, so injected inline styles execute freely. An attacker with access to mailbox settings (admin or agent with mailbox permission) can inject CSS attribute selectors to exfiltrate the CSRF token of any agent/admin who views a conversation in that mailbox. With the CSRF token, the attacker can perform any state-changing action as the victim (create admin accounts, change email/password, etc.) — privilege escalation from agent to admin. This is the result of an incomplete fix of GHSA-jqjf-f566-485j. That advisory reported XSS via mailbox signature. The fix applied `Helper::stripDangerousTags()` to the signature before saving. However, `stripDangerousTags()` only removes `script`, `form`, `iframe`, and `object` tags — it does NOT strip `<style>` tags, leaving CSS injection possible. Version 1.8.213 contains an updated fix.
INFO
Published Date :
April 21, 2026, 3:16 a.m.
Last Modified :
Nov. 11, 2026, 11:10 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
Affected Products
The following products are affected by CVE-2026-40497
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | HIGH | [email protected] |
Solution
- Update FreeScout to version 1.8.213.
- Apply the latest security patches.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-40497.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-40497 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-40497
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-40497 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-40497 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
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CVE Translated by [email protected]
Nov. 11, 2026
Action Type Old Value New Value Added Translation Title: Freescout-help-desk, Description: FreeScout es un help desk autoalojado gratuito y un buzón compartido. Antes de la versión 1.8.213, Helper::stripDangerousTags() de FreeScout elimina “[script_tag]”, “[form]”, “[iframe_tag]”, “[object_tag]” pero NO elimina las etiquetas “[style]”. El campo de firma del buzón se guarda a través de POST /mailbox/settings/{id} y luego se renderiza sin escapar a través de {!! $conversation -> getSignatureProcessed([], true) !!} en las vistas de conversación. CSP permite style-src * ’self’ ’unsafe-inline’, por lo que los estilos en línea inyectados se ejecutan libremente. Un atacante con acceso a la configuración del buzón (administrador o agente con permiso de buzón) puede inyectar selectores de atributos CSS para exfiltrar el token CSRF de cualquier agente/administrador que vea una conversación en ese buzón. Con el token CSRF, el atacante puede realizar cualquier acción que cambie el estado como la víctima (crear cuentas de administrador, cambiar correo electrónico/contraseña, etc.) - escalada de privilegios de agente a administrador. Esto es el resultado de una corrección incompleta de GHSA-jqjf-f566-485j. Esa advertencia informó XSS a través de la firma del buzón. La corrección aplicó Helper::stripDangerousTags() a la firma antes de guardar. Sin embargo, stripDangerousTags() solo elimina las etiquetas script, form, iframe y object - NO elimina las etiquetas “[style]”, dejando posible la inyección CSS. La versión 1.8.213 contiene una corrección actualizada. -
CVE Modified by [email protected]
Jun. 17, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'freescout-help-desk', 'product': 'freescout', 'versions': [{'status': 'affected', 'version': '< 1.8.213'}]}] -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jun. 17, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-40497', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'poc'}, {'automatable': 'no'}, {'technicalImpact': 'total'}], 'version': '2.0.3', 'timestamp': '2026-04-21T13:25:17.184928Z'} -
Initial Analysis by [email protected]
Apr. 23, 2026
Action Type Old Value New Value Added CPE Configuration OR *cpe:2.3:a:freescout:freescout:*:*:*:*:*:*:*:* versions up to (excluding) 1.8.213 Added Reference Type GitHub, Inc.: https://github.com/freescout-help-desk/freescout/commit/5aa8d633216f65995e80a7d4a921b784acc94df4 Types: Patch Added Reference Type GitHub, Inc.: https://github.com/freescout-help-desk/freescout/releases/tag/1.8.213 Types: Release Notes Added Reference Type CISA-ADP: https://github.com/freescout-help-desk/freescout/security/advisories/GHSA-fh99-wr77-pxq3 Types: Vendor Advisory Added Reference Type GitHub, Inc.: https://github.com/freescout-help-desk/freescout/security/advisories/GHSA-fh99-wr77-pxq3 Types: Vendor Advisory -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Apr. 21, 2026
Action Type Old Value New Value Added Reference https://github.com/freescout-help-desk/freescout/security/advisories/GHSA-fh99-wr77-pxq3 -
New CVE Received by [email protected]
Apr. 21, 2026
Action Type Old Value New Value Added Description FreeScout is a free self-hosted help desk and shared mailbox. Prior to version 1.8.213, FreeScout's `Helper::stripDangerousTags()` removes `<script>`, `<form>`, `<iframe>`, `<object>` but does NOT strip `<style>` tags. The mailbox signature field is saved via POST /mailbox/settings/{id} and later rendered unescaped via `{!! $conversation->getSignatureProcessed([], true) !!}` in conversation views. CSP allows `style-src * 'self' 'unsafe-inline'`, so injected inline styles execute freely. An attacker with access to mailbox settings (admin or agent with mailbox permission) can inject CSS attribute selectors to exfiltrate the CSRF token of any agent/admin who views a conversation in that mailbox. With the CSRF token, the attacker can perform any state-changing action as the victim (create admin accounts, change email/password, etc.) — privilege escalation from agent to admin. This is the result of an incomplete fix of GHSA-jqjf-f566-485j. That advisory reported XSS via mailbox signature. The fix applied `Helper::stripDangerousTags()` to the signature before saving. However, `stripDangerousTags()` only removes `script`, `form`, `iframe`, and `object` tags — it does NOT strip `<style>` tags, leaving CSS injection possible. Version 1.8.213 contains an updated fix. Added CVSS V3.1 AV:N/AC:L/PR:H/UI:R/S:C/C:H/I:H/A:N Added CWE CWE-79 Added Reference https://github.com/freescout-help-desk/freescout/commit/5aa8d633216f65995e80a7d4a921b784acc94df4 Added Reference https://github.com/freescout-help-desk/freescout/releases/tag/1.8.213 Added Reference https://github.com/freescout-help-desk/freescout/security/advisories/GHSA-fh99-wr77-pxq3