High · CVSS 7.4CVE-2026-104704

Cleartext Transmission of Sensitive Information in hMailServerCVE-2026-104704

Answer in brief

CVE-2026-104704 records a High severity (CVSS 7.4) vulnerability in Cleartext Transmission of Sensitive Information in hMailServer. The current sources do not mark it as known exploited. The current feed maps Progressive Robot Ltd/hMailServer (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Oct 8, 2026Updated Oct 8, 2026Source checked Oct 8, 2026First seen by HOL Oct 8, 2026Material review Oct 8, 2026

Upstream Advisory

Key facts

Risk: High · CVSS 7.4
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

CVSS is 7.4. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps Progressive Robot Ltd/hMailServer (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
Progressive Robot Ltd/hMailServergeneric	>=6.0.0 <6.3.6	6.3.6

Recommended response

Check inventory. Check lockfiles and deployed manifests for Progressive Robot Ltd/hMailServer.
Review the reported fix. Source-reported solution: Upgrade to hMailServer 6.3.6, which verifies DANE-TA as well as DANE-EE records and requires TLS to a host whose validated TLSA records are all unusable. Until then, an SMTP route for each recipient domain concerned that names its mail exchangers with the connection security 'STARTTLS (required)' prevents delivery in cleartext to that domain.

Evidence timeline and material changes

Published upstream
Oct 8, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Oct 8, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Oct 8, 2026

Sources and claim methodology

Upstream source description

Progressive Robot hMailServer 6.0.0 through 6.3.5 does not enforce TLS for outbound SMTP delivery to a mail exchanger whose DNSSEC-validated TLSA records contain no DANE-EE (usage 3) record, contrary to RFC 7672 section 2.2. The server used only DANE-EE records and treated a validated TLSA record set consisting of DANE-TA (usage 2) or otherwise unusable records as if no records were published, so delivery to such a host fell back to opportunistic TLS. An attacker with an active position on the network path between the server and the recipient's mail exchanger can suppress or break the STARTTLS negotiation and cause messages to be delivered in cleartext, where they can be read and modified.

Quoted source text, attributed separately from HOL analysis.