CVE-2026-126618: Improper Restriction of Excessive Authentication Attempts 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 38% of scored CVEs
DescriptionCVE.org
The auto-ban of Progressive Robot hMailServer 6.0.0-B1 through 6.3.7 can be kept from banning an address after repeated failed logons, which allows a remote unauthenticated attacker who can connect from two or more addresses to go on guessing account passwords - over SMTP AUTH, IMAP and POP3, and over ManageSieve, CalDAV/CardDAV and the REST API where those are turned on (off by default) - without being banned. When the failed logons counted from one address reach MaxInvalidLogonAttempts (3 by default), the server clears that address's count, saves an IP range that refuses the address for AutoBanMinutes (60 by default) and drops the connection. The range is named "Auto-ban: " followed by the user name of the logon that reached the limit, and no two ranges may have the same name. The server chooses the name by checking candidates as written - the name, then the name with a number, a random suffix or a GUID added - and only then cuts it to the 100 characters the database column holds, so that with a user name of 90 characters or more every candidate is the same once cut. While one range named after such a user name stands, every later ban named after a user name with the same first 90 characters therefore fails at the database: no range is saved, the address is not refused, and, its count having already been cleared, it is given the next full set of attempts. A user name of 78 to 89 characters makes later bans fail in the same way: from the second, the third or the twelfth on, depending on its length and the database, or, from 78 to 85 characters, by chance. An attacker who has once had an address banned under such a name can in this way keep guessing passwords from any other address, ending each set of attempts with a logon under a name of that kind; each failed save is reported in the server's error log (as the database error HM5032, and from 6.2.19 also as HM6099).
Affected products1
From the CVE record. A product or version that is not listed is unknown, not unaffected.
- Progressive Robot Ltd · hMailServerfrom 6.0.0-B1 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-2026-126618 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.