{"id":"CVE-2026-114478","state":"PUBLISHED","title":"Unintended Proxy or Intermediary ('Confused Deputy') in hMailServer","description":"Insufficient preservation of the original sender in the forwarding of Progressive Robot hMailServer 6.0.0 through 6.3.6 allows a remote unauthenticated attacker to have mail they write, naming in its From an address at a domain the server hosts, delivered to other receivers as passing that domain's DMARC policy. When the server sent on a copy of mail that came from outside - an account's forward, a mail rule's forward, a Sieve redirect, a list's copy, or an alias or list expanding to an outside address - it could give the copy an SMTP identity in the organisation of the domain the copy's From names, whatever the message's origin: with the Sender Rewriting Scheme or the rewrite of the envelope sender on forwarding enabled (both off by default), an address at the forwarding domain; for a list, its bounce address; for a message with an empty envelope sender, none, under the server's own host name; and an envelope sender the message came with at a subdomain of a hosted domain was kept. Where that identity's SPF record authorises the server, other receivers' SPF check of the copy passed for a domain aligned with the From, and DMARC passed with it, although the message had not passed DMARC when the server received it. Exploitation needs a forward, redirect, alias or list that carries the hosted domain's mail to an outside address, and one of: SRS or the envelope rewrite enabled; a list whose bounce address is in the domain's organisation; an envelope sender at a subdomain whose SPF record authorises the server; or, for an empty envelope sender, an SPF record that authorises the server under its host name. The DKIM route to the same result is CVE-2026-107567.","publishedAt":"2026-10-21T15:12:35.847Z","updatedAt":"2026-10-29T20:55:51.043Z","severity":{"score":5.9,"label":"Medium","version":"3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N","source":"GitLab"},"assigner":"GitLab","products":["Progressive Robot Ltd hMailServer"],"affected":[{"vendor":"Progressive Robot Ltd","product":"hMailServer","defaultStatus":"unaffected","versions":[{"version":"6.0.0","status":"affected","lessThanOrEqual":"6.3.6","versionType":"semver"}],"repo":"https://gitlab.com/hmailserver/hmailserver"}],"references":["https://gitlab.com/hmailserver/hmailserver/-/work_items/90","https://gitlab.com/hmailserver/hmailserver/-/releases/v6.3.7"],"weaknesses":["CWE-441"],"ingestedAt":"2026-10-29T23:14:04.755Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/114xxx/CVE-2026-114478.json","commit":"dc7676b3f67d6707e4927968546e7e0125ff7ec7","baselineCommit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-114478","state":"PUBLISHED","datePublished":"2026-10-21T15:12:35.847Z","dateUpdated":"2026-10-29T20:55:51.043Z","assignerShortName":"GitLab","assignerOrgId":"ceab7361-8a18-47b1-92ba-4d7d25f6715a","dateReserved":"2026-10-21T15:11:45.854Z"},"containers":{"cna":{"title":"Unintended Proxy or Intermediary ('Confused Deputy') in hMailServer","descriptions":[{"lang":"en","value":"Insufficient preservation of the original sender in the forwarding of Progressive Robot hMailServer 6.0.0 through 6.3.6 allows a remote unauthenticated attacker to have mail they write, naming in its From an address at a domain the server hosts, delivered to other receivers as passing that domain's DMARC policy. When the server sent on a copy of mail that came from outside - an account's forward, a mail rule's forward, a Sieve redirect, a list's copy, or an alias or list expanding to an outside address - it could give the copy an SMTP identity in the organisation of the domain the copy's From names, whatever the message's origin: with the Sender Rewriting Scheme or the rewrite of the envelope sender on forwarding enabled (both off by default), an address at the forwarding domain; for a list, its bounce address; for a message with an empty envelope sender, none, under the server's own host name; and an envelope sender the message came with at a subdomain of a hosted domain was kept. Where that identity's SPF record authorises the server, other receivers' SPF check of the copy passed for a domain aligned with the From, and DMARC passed with it, although the message had not passed DMARC when the server received it. Exploitation needs a forward, redirect, alias or list that carries the hosted domain's mail to an outside address, and one of: SRS or the envelope rewrite enabled; a list whose bounce address is in the domain's organisation; an envelope sender at a subdomain whose SPF record authorises the server; or, for an empty envelope sender, an SPF record that authorises the server under its host name. The DKIM route to the same result is CVE-2026-107567."}],"affected":[{"vendor":"Progressive Robot Ltd","product":"hMailServer","defaultStatus":"unaffected","versions":[{"version":"6.0.0","status":"affected","lessThanOrEqual":"6.3.6","versionType":"semver"}],"repo":"https://gitlab.com/hmailserver/hmailserver"}],"references":[{"url":"https://gitlab.com/hmailserver/hmailserver/-/work_items/90"},{"url":"https://gitlab.com/hmailserver/hmailserver/-/releases/v6.3.7"}],"metrics":[{"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}],"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N","attackVector":"NETWORK","attackComplexity":"HIGH","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"NONE","integrityImpact":"HIGH","availabilityImpact":"NONE","baseScore":5.9,"baseSeverity":"MEDIUM"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-441","lang":"en","description":"CWE-441: Unintended Proxy or Intermediary ('Confused Deputy')","type":"CWE"}]}],"providerMetadata":{"shortName":"GitLab","orgId":"ceab7361-8a18-47b1-92ba-4d7d25f6715a","dateUpdated":"2026-10-21T15:12:35.847Z"},"solutions":[{"lang":"en","value":"Upgrade to hMailServer 6.3.7, in which a copy of mail from outside is sent on with an envelope sender, or under a host name, in the organisation of a domain its From names only when the message passed DMARC for that organisation when it arrived, a pass every copy of the message carries. Otherwise a forward, a Sieve redirect or a rule's forward keeps the envelope sender the message came with rather than an SRS or rewritten one; a copy whose identity would still be in that organisation - an empty envelope sender under a host name of it, or an envelope sender at the server's host name or in a hosted domain's organisation - is not sent to an outside address, nor is the message where an alias or a list expands to one; a managed list does not distribute the posting; and a distribution list's bounce address is not applied to it. Until then: keep SRS and the rewrite of the envelope sender on forwarding off where they are not needed; turn on the account option not to forward messages flagged as spam (ForwardAbortSpamFlagged) for accounts that forward to outside addresses, which does not hold a Sieve redirect; and set the DMARC test's score (DMARCFailureScore) at or above the spam delete threshold, so that a message that fails a published quarantine or reject policy is refused, or quarantined, on arrival. Neither of the last two holds mail in the name of a domain whose DMARC policy is none."}],"credits":[{"lang":"en","value":"Found in the hMailServer project's own security review (Progressive Robot Ltd)","type":"finder"}]},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-10-29T17:33:39.332121Z","id":"CVE-2026-114478","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-29T20:55:51.043Z"}}]}}}