CVE-2026-126626: Overly Restrictive Account Lockout Mechanism in hMailServer
Progressive Robot Ltd · hMailServer
Vendor fix available · Affected: Progressive Robot Ltd hMailServer · Exploitation: unlikely (under 1%)
Not in CyberSIXT coverage yet: no article names this CVE. This page shows the public record.
Higher than 44% of scored CVEs
DescriptionCVE.org
The web services listener of Progressive Robot hMailServer 6.3.3 through 6.3.7 counts every failed CardDAV, CalDAV or Autodiscover sign-in from a proxy it trusts - one on the same machine, or one named in WebServicesTrustedProxies, whose X-Forwarded-Proto it believes - against the proxy's own address, which allows a remote unauthenticated attacker who can reach the proxy to have that address banned from the server's mail listeners. The listener, off by default (WebServicesHttpPort and WebServicesHttpsPort 0), signs an account in with HTTP Basic over HTTPS for CardDAV from 6.3.3 and for CalDAV and Outlook Autodiscover from 6.3.4. Behind a TLS-terminating proxy, which the server trusts when it is on the same machine or named in WebServicesTrustedProxies, the listener takes the client's HTTPS from the proxy's X-Forwarded-Proto header, but it does not believe X-Forwarded-For and sees the proxy's address for every client. Each failed sign-in counted towards the auto-ban against that address, so that failed sign-ins through the proxy from anybody, under any user name, reaching MaxInvalidLogonAttempts (3 within 30 minutes by default) wrote an IP range that refused the proxy's address at the SMTP, POP3, IMAP and ManageSieve listeners for AutoBanMinutes (60 by default), and could write it again each time it lapsed. For a proxy on the same machine that address is the loopback address, so that a webmail on that machine, local scripts that submit mail and the other local clients of the mail listeners were shut out; for a proxy at another address that also carries mail, every mail client behind it was. Such a proxy forwarding to the listener's HTTPS port, re-encrypting, was counted against in the same way, and listing it in WebServicesTrustedProxies did not spare it. The auto-ban is on by default and AutoBanNeverBan, which spares an address, is empty by default; the listener itself went on serving the proxy.
Affected products1
From the CVE record. A product or version that is not listed is unknown, not unaffected.
- Progressive Robot Ltd · hMailServerfrom 6.3.3 up to and including 6.3.7
On the Atlas
Every published CVE is on the CyberSIXT Atlas, grouped by weakness, vendor and month.
- Exploitation
- Unlikely (under 1%). EPSS under 1%, or no score yet.
- CISA KEV
- Not listed
- Public check
- No public nuclei template
- Vendor
- Progressive Robot Ltd
- Published
- November 2026
CoverageNo articles yet
No CyberSIXT article names CVE-2026-126626 yet, so there is no coverage timeline, action brief or change log for it. Everything on this page comes from the public CVE record, CISA KEV, EPSS and the nuclei template index. Search the archive or see the CVEs in the news.