CVSS 3.1
5.3 mediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:NCVE-2026-126614 Improper Restriction of Excessive Authentication Attempts in hMailServer
Medium (5.3) in progressive robot ltd hmailserver. EPSS 0.4% estimated probability of exploitation activity in the next 30 days.
On this page
The web services listener of Progressive Robot hMailServer 6.3.3 through 6.3.7 does not apply the server's IP ranges to the connections it accepts, which allows a remote unauthenticated attacker to go on guessing account passwords at the listener's sign-ins after the auto-ban has banned the attacker's address. The listener is off by default (WebServicesHttpPort and WebServicesHttpsPort 0). From 6.3.3 its CardDAV, and from 6.3.4 its CalDAV and its Outlook Autodiscover answer to a request that carries credentials, sign an account in with HTTP Basic over HTTPS. A failed sign-in there counts towards the auto-ban as a failed logon on any other protocol does: when the failures counted from one address reach MaxInvalidLogonAttempts (3 within 30 minutes by default), the server writes an IP range that refuses the address for AutoBanMinutes (60 by default), and the SMTP, POP3, IMAP and ManageSieve listeners refuse it. The web services listener asked no IP range when it accepted a connection (in 6.3.3 nothing, from 6.3.4 the country policy alone), so it went on serving such an address, whether its ban had been earned there or on another protocol, and also an address that an administrator's IP range allowing nothing holds. Each failed sign-in there closed only its own connection, and the next connection was accepted, during the ban and after it. The firewall rule and command the auto-ban can drive (AutoBanFirewall and AutoBanCommand, off by default) are told only the SMTP, POP3 and IMAP ports, so that the firewall rule and the packaged hook did not close the listener's ports, and the fail2ban jail packaged for Linux (off by default) lists only the mail and ManageSieve ports. The only limit left on the guesses at one account there was the per-name lockout (AccountLockoutThreshold in hMailServer.ini, 0, off, by default), which has a separate defect fixed in the same release. The flaw is reached on the listener's HTTPS port: behind a TLS-terminating proxy the listener sees the proxy's address for every client, and a ban never named the client there.
Severity
- EPSS
- 0.4% estimated probability of exploitation activity in the next 30 days; 38th percentile. Scored 2026-11-13. A forecast for this CVE across the internet, not for your own systems.
- CWE
- CWE-307 Improper Restriction of Excessive Authentication Attempts
- OWASP Top 10
- A07:2025 Authentication Failures
- Published
- Modified
- Assigned by
- GitLab (CNA)
- NVD analysis
- Deferred: the NVD does not plan to analyze it
- Record from
- the NVD, synced
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Affected
- progressive robot ltd:hmailserver
Versions
From the CNA's record in the CVE List.
| Product | Affected |
|---|---|
| Progressive Robot Ltd hMailServer | from 6.3.3 through 6.3.7 |
Attack patterns (CAPEC)
- CAPEC-16 Dictionary-based Password Attack Likelihood: Medium · Severity: High
- CAPEC-49 Password Brute Forcing Likelihood: Medium · Severity: High
- CAPEC-560 Use of Known Domain Credentials Likelihood: High · Severity: High
- CAPEC-565 Password Spraying Likelihood: High · Severity: High
- CAPEC-600 Credential Stuffing Likelihood: High · Severity: High
- CAPEC-652 Use of Known Kerberos Credentials Likelihood: Medium · Severity: High
- CAPEC-653 Use of Known Operating System Credentials Likelihood: High · Severity: High
The attack patterns MITRE's CAPEC relates to this record's weaknesses, as MITRE names them. Credits.
History
- The NVD deferred its analysis
Changes since this site first stored the record. The same for every record: /api/public/changes.