hMailServer: Incorrect Default Permissions
CVE-2026-107571 is a high-severity incorrect default permissions vulnerability in hMailServer from Progressive Robot, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. Affected hMailServer versions: 6.0.0 through 6.3.6. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.1% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Check which version of hMailServer you run against the affected versions below, and install the vendor's latest release.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Progressive Robot | hMailServer | 6.0.0 through 6.3.6 | Not stated |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by CNA (gitlab.com).
Official description
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.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Incorrect Default Permissions
During installation, installed file permissions are set to allow anyone to modify those files.
How developers prevent this class of flaw
- The architecture needs to access and modification attributes for files to only those users who actually require those actions.
- Compartmentalize the system to have safe areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area. Ensure that appropriate compartmentalization is built into the system design, and the compartmentalization allows for and reinforces privilege separation functionality. Architects and designers should rely on the principle of least privilege to decide the appropriate time to use privileges and the time to drop privileges.
More Incorrect Default Permissions vulnerabilities (CWE-276)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
Other references
Other vulnerabilities in hMailServer
- 7.3 High severity
- 7.5 High severity
- 7.3 High severity
- 7.5 High severity
- 8.8 High severity
- 7.5 High severity
Recent Incorrect Default Permissions vulnerabilities
- 7.8 High severity
- 7.8 High severity
- 7.1 High severity
- 7.8 High severity
- 8.5 High severity
- 8.4 High severity
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