hMailServer: Improper Link Resolution Before File Access
CVE-2026-126612 is a high-severity improper link resolution before file access 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 6.3.7. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.16% 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 6.3.7 | 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
Improper link resolution in the Windows installer of Progressive Robot hMailServer 6.0.0 through 6.3.7 allows a local authenticated user to run code as the mail server's service account or as an administrator when the path to the program folder passes through a junction, a symbolic link or a mount point that the user controls or that every user may change, such as a junction made at the root of a drive, which takes the root's permissions, or through a folder that every user may rename. Setup installed the programs through any such link without first checking who controls it, or whether a folder above the program folder may be renamed, and the service is registered to run the programs by that path, so the programs are installed where a link another account controls leads, or that account can later make the path lead to a folder it controls; the service, which runs as LocalSystem or as its virtual account, and the programs administrators run from Bin are then started from there. 6.3.7's fix for CVE-2026-107571 does not cover this: its hardening of the program folder, Bin and ControlPanel does not change a folder reached through a link that the administrators do not alone control, and setup does not refuse such a path: it installs through the link and at most reports afterwards that the folders could not be hardened. The default installation under Program Files is not affected.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Link Resolution Before File Access
The product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource.
How developers prevent this class of flaw
- Follow the principle of least privilege when assigning access rights to entities in a software system. Denying access to a file can prevent an attacker from replacing that file with a link to a sensitive file. Ensure good compartmentalization in the system to provide protected areas that can be trusted.
More Improper Link Resolution Before File Access vulnerabilities (CWE-59)
Timeline
- CVE record published.
- 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 Improper Link Resolution Before File Access vulnerabilities
- 9.6 Critical severity
- 7.3 High severity
- 7.8 High severity
- 7.0 High severity
- 7.0 High severity
- 8.1 High severity
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