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CVE-2026-40591— FreeScout: Improper Authorization in Phone Conversation Creation Enables Cross-Mailbox Hidden Customer Modification

Quick assessment

Affected
freescout-help-desk freescout
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

FreeScout是FreeScout公司的一个使用 PHP（Laravel 框架）构建的超轻量级且功能强大的免费开源帮助台和共享收件箱。 FreeScout 1.8.214之前版本存在安全漏洞，该漏洞源于电话对话创建流程接受攻击者控制的customer_id、name、to_email和phone值，并在后端解析目标客户时未强制执行邮箱范围的客户可见性，可能导致可以在邮箱A中创建电话对话的低权限代理将新的邮箱A电话对话绑定到邮箱B的隐藏客户，并通过提供to_email向该隐藏客户记录添加新的别名电子邮件

CVSS 7.1 · High EPSS 0.34% · P25
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I. Basic Information for CVE-2026-40591

Vulnerability Information
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Vulnerability Title
FreeScout: Improper Authorization in Phone Conversation Creation Enables Cross-Mailbox Hidden Customer Modification
Source: CVE Program / CVE List V5
Vulnerability Description
FreeScout is a free self-hosted help desk and shared mailbox. Prior to version 1.8.214, the phone-conversation creation flow accepts attacker-controlled `customer_id`, `name`, `to_email`, and `phone` values and resolves the target customer in the backend without enforcing mailbox-scoped customer visibility. As a result, a low-privileged agent who can create a phone conversation in Mailbox A can bind the new Mailbox A phone conversation to a hidden customer from Mailbox B and add a new alias email to that hidden customer record by supplying `to_email`. Version 1.8.214 fixes the vulnerability.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
通过用户控制密钥绕过授权机制
Source: CVE Program / CVE List V5
Vulnerability Title
FreeScout 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
FreeScout是FreeScout公司的一个使用 PHP（Laravel 框架）构建的超轻量级且功能强大的免费开源帮助台和共享收件箱。 FreeScout 1.8.214之前版本存在安全漏洞，该漏洞源于电话对话创建流程接受攻击者控制的customer_id、name、to_email和phone值，并在后端解析目标客户时未强制执行邮箱范围的客户可见性，可能导致可以在邮箱A中创建电话对话的低权限代理将新的邮箱A电话对话绑定到邮箱B的隐藏客户，并通过提供to_email向该隐藏客户记录添加新的别名电子邮件
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
freescout-help-desk freescout < 1.8.214 -

II. Public POCs for CVE-2026-40591

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III. Intelligence Information for CVE-2026-40591

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Patches & Fixes for CVE-2026-40591 (1)

Vendor Advisories for CVE-2026-40591 (1)

Same Patch Batch · freescout-help-desk · 2026-04-21 · 20 CVEs total

CVE-2026-41193 9.1 CRITICAL FreeScout has Zip Slip path traversal in module installation that allows arbitrary file wr
CVE-2026-40569 9.0 CRITICAL FreeScout's Mass Assignment in Mailbox Connection Settings Enables Silent Email Exfiltrati
CVE-2026-40568 8.5 HIGH FreeScout Vulnerable to XSS via Mailbox Signature Due to Incomplete HTML Sanitization
CVE-2026-40497 8.1 HIGH FreeScout Vulnerable to CSS Injection via Stored Style Tag in Mailbox Signature (CSRF Toke
CVE-2026-40589 7.6 HIGH FreeScout has Customer Edit Cross-Mailbox Email Takeover
CVE-2026-41190 7.1 HIGH FreeScout has assigned-only visibility bypass via save_draft that allows hidden conversati
CVE-2026-41189 7.1 HIGH FreeScout has assigned-only visibility bypass that allows editing hidden customer-authored
CVE-2026-41191 7.1 HIGH FreeScout's signature only mailbox permission allows unauthorized mailbox chat setting cha
CVE-2026-41192 7.1 HIGH FreeScout's client-controlled attachment IDs allow deletion of existing conversation attac
CVE-2026-40565 6.1 MEDIUM FreeScout has Stored XSS / CSS Injection via linkify() — Unescaped URL in Anchor href
CVE-2026-40592 5.9 MEDIUM FreeScout's cross-user undo reply allows mailbox peers to recall another agent's outbound
CVE-2026-40567 5.8 MEDIUM FreeScout has HTML Injection in Outgoing Emails via Unsanitized Customer Name in Signature
CVE-2026-41194 5.4 MEDIUM FreeScout's Mailbox OAuth disconnect uses a state-changing GET and is CSRFable
CVE-2026-41183 4.3 MEDIUM FreeScout allows non-folder conversation queries to disclose assigned-only hidden conversa
CVE-2026-40590 4.3 MEDIUM FreeScout's Customer AJAX Create Modifies Hidden Existing Customer
CVE-2026-40566 4.1 MEDIUM FreeScout vulnerable to SSRF via IMAP/SMTP Connection Test Endpoints
CVE-2026-40570 FreeScout's Missing Authorization in load_customer_info Allows Any Authenticated User to A
CVE-2026-40498 FreeScout has Authentication Bypass and Information Disclosure in SystemController via /sy
CVE-2026-40496 FreeScout has Predictable Attachment Token that Allows Unauthenticated Private File Downlo

IV. Related Vulnerabilities

Same product: freescout
Same vendor: freescout-help-desk
Same weakness: CWE-639

V. Comments for CVE-2026-40591

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