Improper Restriction of Excessive Authentication Attempts in hMailServer (CVE-2026-126614)
Published Last modified Sources: EUVD, CVE.org
What is affected, what to do
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).
The available sources name no fixed version. Check the vendor guidance in the references below.
- Affected
- Progressive Robot hMailServer
lte 6.3.3..6.3.7
- Progressive Robot hMailServer
Not sure whether and how you are affected? Ask a question about this vulnerability
Metrics
5.3
XIEM Effective CVSS
Highest available CVSS rating from NVD and vendor data.
Source: Vendor (CNA), CVSS v3
5.3
CVSS v3
Severity Medium on the scale from 0 to 10.
Source: EUVD, CVE.org
0.4 %
EPSS score
Low — model estimates < 1% exploitation likelihood.
Source: FIRST EPSS, percentile 38.0
Show all metrics
- Severity
- Medium
Priority (0–325)
The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?
Read in glossary- 68.07 Methodology
Exploit maturity
An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.
Read in glossary- no public PoC known
XIEM Effective CVSS
XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.
Read in glossary- 5.3 Methodology
CVSS v3
CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.
Read in glossary- 5.3
EPSS score
The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.
Read in glossary- 0.4 %
- Low — model estimates < 1% exploitation likelihood.
EPSS percentile
The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.
Read in glossary- 38.0
- High — this CVE ranks above the median of all CVEs scored today (rank ≥ 36%).
KEV status
The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.
Read in glossary- —
- Published
CWE
CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.
Read in glossary- CWE-307
Detection rules
No NEOSEC detection rule is available for this vulnerability yet.
Classification under NIS2 and CRA
Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.
NIS2
NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.
Read in glossary- Handle the vulnerability in regular vulnerability handling under Art. 21(2)(e) NIS2.
CRA
The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.
Read in glossary- From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
ISO/IEC 27001
ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.
Read in glossary- Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.
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.
Source: ENISA EUVD, cvelistv5, NVD (NIST), CVE.org (MITRE)
Affected products
The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.
| Affected versions | Fixed in | ||
|---|---|---|---|
| Progressive Robot Ltd | hMailServer |
|
|
Vendors and products
Weakness classes (CWE)
CWE-307Improper Restriction of Excessive Authentication Attempts
Base
The product does not implement sufficient measures to prevent multiple failed authentication attempts within a short time frame.
Entry at MITRE CWE-307
References & sources
- gitlab.comhmailserver/hmailserver/-/work_items/105euvd
- gitlab.comhmailserver/hmailserver/-/releases/v6.3.8euvd
- NVD (NIST)vuln/detail/CVE-2026-126614euvd
Changes to this CVE
Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).
ReceivedGitLab
CVSS V3.1: AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Weakness type: CWE-307
Description added or changed
Show 6 original changes
Individual changes of this event as published by NVD Type Action Before After Description added —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.CVSS added —AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:NWeakness type (CWE) added —CWE-307Affected versions (publisher) added —New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/126xxx/CVE-2026-126614.json">CVE-2026-126614</a>Reference added —https://gitlab.com/hmailserver/hmailserver/-/releases/v6.3.8Reference added —https://gitlab.com/hmailserver/hmailserver/-/work_items/105Source identifier: cve@gitlab.com
Embed badge
Show the severity and KEV status of this vulnerability on your site – with a link back here. The image is updated hourly.
<a href="https://intel.neosec.eu/en/cve/CVE-2026-126614"><img src="https://intel.neosec.eu/badge/cve/CVE-2026-126614.svg?lang=en" alt="CVE-2026-126614 – NEOSEC Intel" height="20"></a>