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Back to active CVEs
Medium · CVSS 5.9CVE-2026-114478

Unintended Proxy or Intermediary ('Confused Deputy') in hMailServerCVE-2026-114478

Answer in brief

CVE-2026-114478 records a Medium severity (CVSS 5.9) vulnerability in Unintended Proxy or Intermediary ('Confused Deputy') 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 21, 2026Updated Oct 21, 2026Source checked Oct 21, 2026First seen by HOL Oct 21, 2026Material review Oct 21, 2026
Upstream Advisory

Key facts

Risk
Medium · CVSS 5.9
Exploitation
Not marked as known exploited
Affected software
1 mapped package or product
Fix availability
Not reported

Why this deserves its current priority

CVSS is 5.9. 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
PackageAffected rangeFixed version
Progressive Robot Ltd/hMailServergeneric>=6.0.0 <=6.3.6Not reported

Recommended response

  1. 1Check inventory. Check lockfiles and deployed manifests for Progressive Robot Ltd/hMailServer.
  2. 2Review the reported fix. Source-reported solution: 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.

Evidence timeline and material changes

  1. Published upstream

    Oct 21, 2026

    Evidence: source:cvelist:source_dates:source-dates:record
  2. Source modified

    Oct 21, 2026

    Evidence: source:cvelist:source_dates:source-dates:record
  3. First seen by HOL

    Oct 21, 2026

Sources and claim methodology

  • Source referencegitlab.com
  • Source referencegitlab.com
Upstream source 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.

Quoted source text, attributed separately from HOL analysis.

Related CVEs

  • Incorrect Authorization in hMailServerSame progressive robot ltd/hmailserver package

Record context

Vulnerability class
SSRF
EPSS
Not reported
CWE IDs
CWE-441
Source
CVE List V5
Source checked
Oct 21, 2026
References
2 linked sources
Open source record