---
title: "CVE-2026-107569: Progressive Robot hMailServer - Denial of Service"
description: "Progressive Robot hMailServer 6.0.0 through 6.3.6 contains a denial of service caused by improper validation of the X-hMailServer-LoopCount header in mail forwarding logic, letting remote unauthenticated attackers stop mail service by triggering infinite mail loops, exploit requires sending crafted emails with manipulated LoopCount header."
url: https://panop.io/threat-heartbeat/CVE-2026-107569/
---

# CVE-2026-107569 Progressive Robot hMailServer - Denial of Service

Progressive Robot hMailServer 6.0.0 through 6.3.6 contains a denial of service caused by improper validation of the X-hMailServer-LoopCount header in mail forwarding logic, letting remote unauthenticated attackers stop mail service by triggering infinite mail loops, exploit requires sending crafted emails with manipulated LoopCount header.

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-2026-107569)

## Details

Type

Denial of Service

Impact

Denial Of Service

CVSS vector

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

Published

19 October 2026

Updated

20 October 2026

Weakness

[CWE-606](https://cwe.mitre.org/data/definitions/606.html)

## Vendor fix

Update to a version later than 6.3.6 or the latest available version.

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-2026-107569](https://nvd.nist.gov/vuln/detail/CVE-2026-107569)
- [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/81](https://gitlab.com/hmailserver/hmailserver/-/work_items/81)

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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

Panop answers these inside your environment, for this CVE and every other finding.

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