CVE-2026-104659 Origin Validation Error in hMailServer
Remote attackers can brute-force admin passwords via DNS rebinding due to missing host validation and throttling, gaining full administrative control.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-104659?
CVE-2026-104659 is a high-severity authentication bypass vulnerability in Progressive Robot Ltd hMailServer, published on 8 Oct 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
Missing Host header validation and missing throttling of failed administrator sign-ins in the REST API listener of Progressive Robot hMailServer 6.0.0 through 6.3.5 allow a remote attacker to brute-force the server administrator's password through the administrator's own browser by DNS rebinding. The listener, which is off by default and bound to the loopback when enabled, answered requests whatever their Host header named, and a failed sign-in with the administrator's password from the loopback was neither auto-banned nor delayed. A web page whose host name the attacker rebinds to 127.0.0.1, opened in a browser on the server, can therefore send authenticated requests to the listener, read the answers and try administrator passwords at full speed until one is accepted, giving the attacker full administrative control of the mail server.
Weakness: CWE-346
Which versions are affected by CVE-2026-104659?
How do I fix CVE-2026-104659?
No fix has been published for CVE-2026-104659 yet. Limit exposure of the affected software until one is available.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-104659 being exploited?
There is no known exploitation of CVE-2026-104659 in the wild and no public exploit code.
Sources
Also known as GHSA-7264-4fp3-6f67.