Overly Restrictive Account Lockout Mechanism in hMailServer
- Exploited
- No known exploitation
- Fix
- No fix listed
- Who is exposed
- Not reported
- Published
- Last modified
- Whether it needs action now or is a reference record, by fixed rules, with why. Last checked is when cve.now last re-read it.What do these mean? →
- Reference
- Last checked
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 27/100 · provisional
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
Progressive Robot hMailServer's web services listener lets a remote attacker, without logging in, get the address of a proxy it trusts banned from the server's SMTP, POP3, IMAP and ManageSieve listeners by making failed sign-in attempts through that proxy. This blocks every mail client that reaches the server through the proxy, including local webmail and scripts on the same machine.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
Read the original description
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.
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure17/25No login or user action needed per the CVSS vector, reachable over the network without a login · Unknown: No advisory context yet
- Reach?/20Unknown. No tracked technology or package matched
- Severity5.3/10CVSS 5.3
- No patch5/5No patch listed yet
What would change the score
- Would score about 72 if added to CISA KEV
- Would score about 67 if CISA's SSVC rates exploitation active
- Would score about 32 if advisories confirm default setups are exposed
Check your systems with an agent
Paste this into a coding or ops agent. It checks your systems read-only and reports a table per asset.
Check whether my systems are affected by CVE-2026-126626 (Overly Restrictive Account Lockout Mechanism 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-2026-126626 (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-2026-126626 is not listed as of cve.now's last read. This KEV status is for CVE-2026-126626 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/106 - 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-2026-126626 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-2026-126626.
Timeline
- CVE published
- First seen by cve.now
Affected versions
- Progressive Robot Ltd hMailServer
From 6.3.3 · through 6.3.7
Evidence 4
CVE record · 2
Establishes: The identifier and description.
- Record
- Record
Corrections
None so far.
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Questions about CVE-2026-126626
Is CVE-2026-126626 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: cve.now feed data
Which versions are affected by CVE-2026-126626?
hMailServer: from 6.3.3 through 6.3.7.Source: cve.now feed data