CVE-2026-104659

Status: DeferredHigh (7.5)—

Missing Host header validation and missing throttling of failed administrator sign-ins in the REST API listener of Progressive Robot hMailServer 6.0.0 through 6.3.5 allow a remote attacker to brute-force the server administrator's password through the administrator's own browser by DNS rebinding. The listener, which is off by default and bound to the loopback when enabled, answered requests whatever their Host header named, and a failed sign-in with the administrator's password from the loopback was neither auto-banned nor delayed.

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A web page whose host name the attacker rebinds to 127.0.0.1, opened in a browser on the server, can therefore send authenticated requests to the listener, read the answers and try administrator passwords at full speed until one is accepted, giving the attacker full administrative control of the mail server.

CVSS

Version: 3.1
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
Base score: 7.5

Exploitation probability (EPSS)

Probability of exploitation in the next 30 days: 0.14%
Percentile among all scored CVEs: 3
Score date: 10/13/2026

EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).

🎯 ATT&CK techniques

How this vulnerability is exploited and what the attacker gains, in MITRE ATT&CK terms.

ExploitationT1203 Exploitation for Client Executionexecution60 %

Inferred by deterministic rules from the CVSS vector and CWE. Indicative only.

🛡️ ATT&CK mitigations that cover these techniques

Application Isolation and Sandboxing Exploit Protection Update Software

Affected technologies (1)

⚠ AI-inferred from the description — NVD hasn't analyzed this CVE yet, these aren't verified CPEs.

Hmailserver — Hmailserver^AI

CWEs

CWE-346

References

Raw JSON (NVD)

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        {
          "repo": "https://gitlab.com/hmailserver/hmailserver",
          "vendor": "Progressive Robot Ltd",
          "product": "hMailServer",
          "versions": [
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              "version": "6.0.0",
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  "published": "2026-10-08T11:16:44.013",
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  "lastModified": "2026-10-08T21:02:43.860",
  "sourceIdentifier": "cve@gitlab.com"
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