Cleartext Transmission of Sensitive Information in hMailServer

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-104704
StatePUBLISHED
AssignerGitLab
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-08 11:16:44 UTC
Updated2026-10-08 21:02:43 UTC
DescriptionProgressive 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.

Risk And Classification

Primary CVSS: v3.1 7.4 HIGH from [email protected]

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

EPSS: 0.001500000 probability, percentile 0.036960000 (date 2026-10-10)

Problem Types: CWE-319 | CWE-319 CWE-319: Cleartext Transmission of Sensitive Information

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary7.4HIGHCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
3.1CNACVSS7.4HIGHCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Progressive Robot Ltd HMailServer affected 6.0.0 6.3.6 semver Not specified

References

ReferenceSourceLinkTags
gitlab.com/hmailserver/hmailserver/-/work_items/61 [email protected] gitlab.com
gitlab.com/hmailserver/hmailserver/-/releases/v6.3.6 [email protected] gitlab.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Found in the hMailServer project's own security review (Progressive Robot Ltd) (en)

Additional Advisory Data

Solutions

CNA: 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.

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