Improper Link Resolution Before File Access ('Link Following') in hMailServer
Summary
| CVE | CVE-2026-107578 |
|---|---|
| State | PUBLISHED |
| Assigner | GitLab |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-10-08 12:17:15 UTC |
| Updated | 2026-10-08 21:02:43 UTC |
| Description | Improper link resolution and external control of file paths in the administrative command-line operations of hMailServer.exe in Progressive Robot hMailServer 6.3.4 and 6.3.5 allow a local attacker who already runs code as the low-privilege service account to escalate privilege. On Windows, operations run with administrator rights by the installer, DBSetup, the Control Panel or an administrator wrote log entries and crash records into the log folder, created, deleted and changed the permissions of the self-signed certificate and private key in the data folder, and rewrote message files in the data folder, all by path in folders the service account (NT SERVICE\hMailServer, the default for new installations since 6.3.4) can modify, following junctions and mount points; and the store-maintenance operations reached files by names taken from the database, which the service account can write, including names outside the data folder. On Linux, the store-maintenance and object-storage operations run as root followed symbolic links the service account (the packaged hmailserver user, which owns the data folder) planted in it, so a root-run operation read, wrote or removed the link's target as root. A local attacker controlling the service account can thereby gain the administrator's (Windows) or root's (Linux) privileges when such an operation is run. |
Risk And Classification
Primary CVSS: v3.1 6.7 MEDIUM from [email protected]
CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H
EPSS: 0.000730000 probability, percentile 0.000670000 (date 2026-10-10)
Problem Types: CWE-59 | CWE-59 CWE-59: Improper Link Resolution Before File Access ('Link Following')
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 3.1 | [email protected] | Secondary | 6.7 | MEDIUM | CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H |
| 3.1 | CNA | CVSS | 6.7 | MEDIUM | CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H |
CVSS v3.1 Breakdown
CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Progressive Robot Ltd | HMailServer | affected 6.3.4 6.3.6 semver | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| gitlab.com/hmailserver/hmailserver/-/releases/v6.3.6 | [email protected] | gitlab.com | |
| gitlab.com/hmailserver/hmailserver/-/work_items/71 | [email protected] | gitlab.com | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: Found in the hMailServer project's own security review (Progressive Robot Ltd) (en)
Additional Advisory Data
Solutions
CNA: Upgrade to hMailServer 6.3.6, in which every administrative command writes nothing to the logs and arms no crash recorder, writes the certificate only through folders held open and checked from the drive's root, reaches no file a database row names outside the data folder, and walks the data folder before any store command - going through a junction or mount point only when the administrators alone own and control it and refusing any other; and on Linux a store or object-storage command run as root first drops to the service account, so it follows no link that account planted. Until then: on Windows run the service as LocalSystem, or stop the service and check the program folder's Logs, Data, Temp and Database folders for junctions, mount points and symbolic links and that no message row names a path outside the data folder; on Linux run the store commands only as the service user, never as root.