CVE-2026-39384Public exploitNetwork attack vector

Cross-mailbox data modification via unchecked merge target

Published Apr 7, 2026 · Updated Apr 7, 2026

Authorization bypass in FreeScout before 1.8.212 allows remote authenticated users to merge customers hidden in other mailboxes. CustomersController::mergeSave resolves the supplied customer2_id without enforcing the limited user's visibility boundary before completing the merge. Exploitation requires APP_LIMIT_USER_CUSTOMER_VISIBILITY to be enabled and an agent account; it deletes the hidden target and reassigns its email and conversations.

CVSS severity7.6
High
EPSS probability0.24%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authorization bypass in FreeScout before 1.8.212 allows remote authenticated users to merge customers hidden in other mailboxes. CustomersController::mergeSave resolves the supplied customer2_id without enforcing the limited user's visibility boundary before completing the merge. Exploitation requires APP_LIMIT_USER_CUSTOMER_VISIBILITY to be enabled and an agent account; it deletes the hidden target and reassigns its email and conversations.

The record

CVE
CVE-2026-39384
Published
Apr 7, 2026
Updated
Apr 7, 2026
Vendor
FreeScout
Product
FreeScout
Classifications
CWE-639, T1190
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 7, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 7, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 1.8.212

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

FreeScout · FreeScoutversion=< 1.8.212

Published CVSS scores

7.6GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-639Authorization Bypass Through User-Controlled Key
T1190Exploit Public-Facing Application

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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