CVE-2026-114473

Incorrect Authorization in hMailServer

Published Oct 21, 2026 CVSS 3.1 · 5 Medium EPSS < 1% KEV · Not listed
Description
Incorrect authorization in the Sender Rewriting Scheme (SRS) of Progressive Robot hMailServer 6.2.1 through 6.3.6 allows a remote attacker to relay mail through the server to outside addresses. With SRS enabled, the server rewrites the envelope sender of mail it forwards to a signed SRS address at the forwarding domain, and passes a bounce to that address back to the original sender; but it took every message to a valid SRS address, whatever its sender, as delivery to a local recipient, so the relay rules and the SMTP authentication they require were not applied, and the message was delivered to the outside address the SRS address encodes. Anyone holding a valid SRS address of the server, such as the recipient of a forwarded message, could have the server relay mail to the address it encodes for 21 days, and an account holder whose account forwards to an outside mailbox could obtain one for any address. SRS is off by default.

Remediation

Vendor Solution

Upgrade to hMailServer 6.3.7, which takes only a bounce (a null reverse-path) to an SRS address as local delivery and holds any other message to it to the relay rules: where they refuse it, the transaction is refused at DATA or BDAT, and a recipient named after such an address in the same transaction is answered 452 4.5.3. Until then, turn SRS off (SRSEnabled=0, the default).

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Progressive Robot
Progressive Robot hmailserver
Vendors & Products Progressive Robot
Progressive Robot hmailserver
Type Values Removed Values Added
Description Incorrect authorization in the Sender Rewriting Scheme (SRS) of Progressive Robot hMailServer 6.2.1 through 6.3.6 allows a remote attacker to relay mail through the server to outside addresses. With SRS enabled, the server rewrites the envelope sender of mail it forwards to a signed SRS address at the forwarding domain, and passes a bounce to that address back to the original sender; but it took every message to a valid SRS address, whatever its sender, as delivery to a local recipient, so the relay rules and the SMTP authentication they require were not applied, and the message was delivered to the outside address the SRS address encodes. Anyone holding a valid SRS address of the server, such as the recipient of a forwarded message, could have the server relay mail to the address it encodes for 21 days, and an account holder whose account forwards to an outside mailbox could obtain one for any address. SRS is off by default.
Title Incorrect Authorization in hMailServer
Weaknesses CWE-863
References
Metrics cvssV3_1

{'score': 5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:L/A:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitLab
Published
Updated
Oct 29, 2026, 8:56 PM
Reserved
Oct 21, 2026, 3:11 PM
Status
Awaiting Analysis
Published
Oct 21, 2026, 4:17 PM
Modified
Oct 29, 2026, 9:17 PM