---
title: "CVE-2026-107567: Progressive Robot hMailServer - Authentication Bypass"
description: "Progressive Robot hMailServer 6.0.0 through 6.3.6 contains a broken authentication caused by DKIM signing messages based solely on the From header without sender authentication, letting remote unauthenticated attackers forge signed emails for hosted domains, exploit requires DKIM signing enabled and mail forwarding to external addresses."
url: https://panop.io/threat-heartbeat/CVE-2026-107567/
---

# CVE-2026-107567 Progressive Robot hMailServer - Authentication Bypass

Progressive Robot hMailServer 6.0.0 through 6.3.6 contains a broken authentication caused by DKIM signing messages based solely on the From header without sender authentication, letting remote unauthenticated attackers forge signed emails for hosted domains, exploit requires DKIM signing enabled and mail forwarding to external addresses.

CVSS base score 7.5 /10

High

CISA KEV

Not listed

Public exploit

None known

Authentication

Not required

[View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-107567)

## Details

Type

Authentication Bypass

Impact

Broken Authentication

CVSS vector

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

Published

19 October 2026

Updated

20 October 2026

Weakness

[CWE-348](https://cwe.mitre.org/data/definitions/348.html)

## Vendor fix

Update to a version later than 6.3.6 or apply patches that enforce sender authentication before DKIM signing.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

## References

- [https://nvd.nist.gov/vuln/detail/CVE-2026-107567](https://nvd.nist.gov/vuln/detail/CVE-2026-107567)
- [https://gitlab.com/hmailserver/hmailserver/-/releases/v6.3.7](https://gitlab.com/hmailserver/hmailserver/-/releases/v6.3.7)
- [https://gitlab.com/hmailserver/hmailserver/-/work\_items/84](https://gitlab.com/hmailserver/hmailserver/-/work_items/84)

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## What this record can't tell you

- Whether you run the affected software, and where
- Whether an attacker can actually reach and exploit it
- The misconfigurations that never get a CVE number
- What it would cost the business, ranked into what to fix first

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