---
id: "CVE-2026-107571"
kind: "vulnerability"
aliases: ["CVE-2026-107571"]
title: "hMailServer installer: non-default folder lets local users run code as SYSTEM"
severity: "high"
cvss: 7.8
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["hmailserver", "mail-server", "package", "windows"]
not_affected_if: ["default-config", "program-files-install"]
published_at: "2026-10-19T16:17:01+00:00"
first_seen_at: "2026-10-23T21:57:18+00:00"
updated_at: "2026-10-25T03:10:15+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-107571", "first_seen_at": "2026-10-23T21:57:18+00:00"}]
---

# hMailServer installer: non-default folder lets local users run code as SYSTEM

hMailServer 6.0.0 through 6.3.6 installed to a folder that inherits writable permissions, such as a drive root, lets a local user without admin rights replace server programs. The attacker gains code execution with LocalSystem or the service's virtual account privileges.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Find the hMailServer install path (default is under Program Files); if it sits at a drive root or any folder inheriting write access for Authenticated Users or Users, it is exposed.
- Check the folder ACL with `icacls "C:\path\to\hMailServer"` and look for Authenticated Users (M) or Users (CI)(AD) write rights.
- Confirm the installed version is in the range 6.0.0 through 6.3.6.

## Fix

- Upgrade hMailServer to a version after `6.3.6` (fixed version unknown from sources).
- Reinstall hMailServer under the default Program Files path, which the sources say is not affected.
- Remove write permissions for Authenticated Users and Users from the install folder and its Bin subfolder.

## Timeline

- 2026-10-23T21:57:18+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-107571

## From the sources

Incorrect default permissions in the Windows installer of Progressive Robot hMailServer 6.0.0 through 6.3.6 allow a local authenticated user to run code as the mail server's high-privileged accounts when the product is installed in a folder whose permissions are inherited from a writable parent, such as the root of a drive. The installer places the server's programs in the Bin folder of the program folder and gives neither the program folder nor Bin any permissions of their own, so they inherit the parent's. Under the default location, Program Files, ordinary users receive only read and execute and the configuration is not affected; but the installer accepts any path without warning, and a program folder at the root of an NTFS volume inherits write access for a broad group - Authenticated Users (Modify) on a Windows client, Users (create files and folders) on Windows Server. A local user without administrator rights can then alter or replace the service program, which runs as LocalSystem or as the service's virtual account, or the programs an administrator runs elevated from Bin during setup and maintenance, or place a library in Bin that those programs load in place of the system copy, gaining code execution with those privileges. The default Program Files installation is not affected.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_