# CVE-2026-40497: FreeScout Vulnerable to CSS Injection via Stored Style Tag in Mailbox Signature (CSRF Token Exfiltration)

> Attackers can inject CSS to steal CSRF tokens, enabling privilege escalation from agent to admin in FreeScout help desk.

- **Severity:** High 8.1 (`CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 21 Apr 2026
- **Updated:** 21 Apr 2026
- **Also known as:** GHSA-fh99-wr77-pxq3

## What is CVE-2026-40497?

CVE-2026-40497 is a high-severity cross-site scripting vulnerability in freescout-help-desk freescout, published on 21 Apr 2026. An attacker needs administrator access to exploit it, and only if a user opens a file or follows a link.

### Official 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.

Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2026-40497?

It affects 1 product.


Products: Freescout Freescout.

## How do I fix CVE-2026-40497?

No fix has been published for CVE-2026-40497 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-40497 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-40497 exists.

## Other vulnerabilities in freescout-help-desk freescout

- [CVE-2026-28289](https://insights.sbomify.com/CVE-2026-28289/): FreeScout 1.8.206 Patch Bypass for CVE-2026-27636 via Zero-Width Space Character Leads to Remote Code Execution (critical 10.0)
- [CVE-2026-27637](https://insights.sbomify.com/CVE-2026-27637/): FreeScout's Predictable Authentication Token Enables Account Takeover (critical 9.8)
- [CVE-2026-32754](https://insights.sbomify.com/CVE-2026-32754/): FreeScout: Stored XSS via Unescaped Email Template Rendering ({!! $thread->body !!}) (critical 9.3)
- [CVE-2024-29185](https://insights.sbomify.com/CVE-2024-29185/): FreeScout OS Command Injection vulnerability (critical 9.1)
- [CVE-2026-40498](https://insights.sbomify.com/CVE-2026-40498/): FreeScout has Authentication Bypass and Information Disclosure in SystemController via /system/cron (high 8.9)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-40497 and fix it if it is affected.

What it is: CVE-2026-40497 is a high-severity cross-site scripting vulnerability in freescout-help-desk freescout, published on 21 Apr 2026. An attacker needs administrator access to exploit it, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-40497 exists.

Affected product: freescout-help-desk freescout. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-40497/ (Markdown: https://insights.sbomify.com/CVE-2026-40497/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-40497
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-40497
- OSV: https://osv.dev/vulnerability/CVE-2026-40497

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-40497/
Summaries are generated and may contain mistakes; the official description above is the record.