CVE-2026-104658: CWE-807: Reliance on Untrusted Inputs in a Security Decision in Progressive Robot Ltd hMailServer
Description
CVE-2026-104658 is a high-severity vulnerability in Progressive Robot Ltd's hMailServer versions 6.3.4 and 6.3.5. The Linux live-update helper (hmailserver-update) runs as root and processes a request file created by the unprivileged hmailserver service account. This design flaw allows an attacker with code execution as the service account to escalate privileges to root by manipulating the update verification process. The vulnerability affects installations where the live update systemd unit is active, which is the default for .deb and .rpm packages and AppImage installations run under that unit.
CVSS v3.1
Score 7.8high
Affected software
Progressive Robot Ltd
hMailServer
pkg:deb/progressive-robot/hmailserverRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability arises from the hmailserver-update helper running as root and relying on untrusted input from the hmailserver service account to determine the program used for verifying AppImage update signatures and the systemd unit to stop before reading service account files. An attacker who already has code execution as the hmailserver service account can exploit this to execute arbitrary code with root privileges on Linux systems where the live update path unit is active. This affects hMailServer versions 6.3.4 and 6.3.5, prior to 6.3.6.
Potential Impact
Successful exploitation allows an attacker with limited privileges (hmailserver service account) to escalate to root privileges, potentially leading to full system compromise. The vulnerability impacts confidentiality, integrity, and availability, as indicated by the CVSS vector (C:H/I:H/A:H).
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, restrict access to the hmailserver service account and disable the live update systemd unit if not required to reduce exposure.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitLab
- Date Reserved
- 2026-10-02T07:38:54.248Z
- Cvss Version
- 3.1
- State
- PUBLISHED
Threat ID: 6ac778a32cdf04f6560ccf51
Added to database: 10/08/2026, 11:04:03 UTC
Last enriched: 10/08/2026, 11:18:33 UTC
Last updated: 10/08/2026, 11:19:29 UTC
Views: 4
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