CVE-2026-40591 FreeScout: Improper Authorization in Phone Conversation Creation Enables Cross-Mailbox Hidden Customer Modification
Low-privileged agents can modify hidden customer records in other mailboxes by manipulating phone conversation creation parameters.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-40591?
CVE-2026-40591 is a high-severity missing authorization vulnerability in freescout-help-desk freescout, published on 21 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official 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.
Weakness: CWE-639
Which versions are affected by CVE-2026-40591?
How do I fix CVE-2026-40591?
No fix has been published for CVE-2026-40591 yet. Limit exposure of the affected software until one is available.
Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.
Is CVE-2026-40591 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-40591 exists.
Sources
Also known as GHSA-9ff4-mmhv-x6jp.