CVE-2026-104704

Published

08 October 2026

Modified

08 October 2026

CVSS Score v3.1 7.4

Click a component to see what it means

Raw vector

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

EPSS Score 0.0015 4th percentile

Risk Priority 53 floored blend · peak EPSS

CVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.

Summary

CVE-2026-104704 is a high-severity Cleartext Transmission of Sensitive Information (CWE-319) vulnerability. Its CVSS base score is 7.4 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Network Sniffing (T1040); ranked at the 4th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified map to SC-8 (Transmission Confidentiality and Integrity) — see the control section below for these in your framework.

OWASP Top 10 for Web (2025)

EU & UK References

🇪🇺 ENISA EUVD: EUVD-2026-94831

Vulnerability Data

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.

CWE(s): CWE-319

Related Threats

MITRE ATT&CK Enterprise Techniques

T1040 Network Sniffing Credential Access

Adversaries may passively sniff network traffic to capture information about an environment, including authentication material passed over the network.

attack.mitre.org →

Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2024-38891Shared CWE-319

CVE-2026-22544Shared CWE-319

CVE-2026-10584Shared CWE-319

CVE-2023-1656Shared CWE-319

CVE-2025-61738Shared CWE-319

CVE-2024-9620Shared CWE-319

CVE-2026-55844Shared CWE-319

CVE-2026-24212Shared CWE-319

CVE-2023-25437Shared CWE-319

CVE-2024-30209Shared CWE-319

Affected Assets

Mitigating Controls

Mitigating Controls (NIST 800-53 r5) AI

SC-8 Transmission Confidentiality and Integrity partial match

SC-8 directly requires protecting confidentiality of transmitted information, which structurally eliminates cleartext transmission of sensitive data.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.DS-02 partial match

blocks

Encryption of data-in-transit directly prevents cleartext transmission while the control also addresses integrity and availability.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.5.14 Information transfer partial match

blocks

Mandating cryptographic protection and stronger authentication on public networks stops the transmission of plaintext sensitive information.

A.5.15 Access control partial match

removes

A.5.16 Identity management partial match

removes

A.5.17 Authentication information partial match

removes

A.5.18 Access rights partial match

removes

A.8.10 Information deletion partial match