CVE-2026-104659 Progressive Robot hMailServer - Authentication Bypass

Progressive Robot hMailServer 6.0.0 through 6.3.5 contains a broken authentication caused by missing Host header validation and lack of throttling on failed admin sign-ins in the REST API listener, letting remote attackers perform brute-force attacks via DNS rebinding, exploit requires attacker to control a web page opened in the administrator's browser.

CVSS base score 7.5 /10
High
CISA KEV
Not listed
Public exploit
None known
Authentication
Not required
EPSS
0.14% chance of exploitation in 30 days
View the NVD record ↗

Details

Type
Authentication Bypass
Impact
Broken Authentication
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
Published
8 October 2026
Updated
15 October 2026
Weakness
CWE-346

Vendor fix

Update to a version later than 6.3.5 or apply patches that validate Host headers and implement throttling on failed sign-ins.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

References

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