CVE-2026-114478 (GCVE-0-2026-114478)
Vulnerability from cvelistv5 – Published: 2026-10-21 15:12 – Updated: 2026-10-29 20:55
VLAI
EPSS
VEX
Title
Unintended Proxy or Intermediary ('Confused Deputy') in hMailServer
Summary
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.
Severity
5.9 (Medium)
SSVC
Exploitation: none
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-10-29 17:33 UTC
CWE
- CWE-441 - Unintended Proxy or Intermediary ('Confused Deputy')
Assigner
References
Impacted products
1 product
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| Progressive Robot Ltd | hMailServer |
Affected:
6.0.0 , ≤ 6.3.6
(semver)
|
guessed |
{
"containers": {
"adp": [
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2026-114478",
"options": [
{
"Exploitation": "none"
},
{
"Automatable": "no"
},
{
"Technical Impact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-10-29T17:33:39.332121Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-10-29T20:55:51.043Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"product": "hMailServer",
"repo": "https://gitlab.com/hmailserver/hmailserver",
"vendor": "Progressive Robot Ltd",
"versions": [
{
"lessThanOrEqual": "6.3.6",
"status": "affected",
"version": "6.0.0",
"versionType": "semver"
}
]
}
],
"credits": [
{
"lang": "en",
"type": "finder",
"value": "Found in the hMailServer project\u0027s own security review (Progressive Robot Ltd)"
}
],
"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\u0027s DMARC policy. When the server sent on a copy of mail that came from outside - an account\u0027s forward, a mail rule\u0027s forward, a Sieve redirect, a list\u0027s 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\u0027s From names, whatever the message\u0027s 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\u0027s own host name; and an envelope sender the message came with at a subdomain of a hosted domain was kept. Where that identity\u0027s SPF record authorises the server, other receivers\u0027 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\u0027s mail to an outside address, and one of: SRS or the envelope rewrite enabled; a list whose bounce address is in the domain\u0027s 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."
}
],
"metrics": [
{
"cvssV3_1": {
"attackComplexity": "HIGH",
"attackVector": "NETWORK",
"availabilityImpact": "NONE",
"baseScore": 5.9,
"baseSeverity": "MEDIUM",
"confidentialityImpact": "NONE",
"integrityImpact": "HIGH",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N",
"version": "3.1"
},
"format": "CVSS",
"scenarios": [
{
"lang": "en",
"value": "GENERAL"
}
]
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-441",
"description": "CWE-441: Unintended Proxy or Intermediary (\u0027Confused Deputy\u0027)",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-10-21T15:12:35.847Z",
"orgId": "ceab7361-8a18-47b1-92ba-4d7d25f6715a",
"shortName": "GitLab"
},
"references": [
{
"url": "https://gitlab.com/hmailserver/hmailserver/-/work_items/90"
},
{
"url": "https://gitlab.com/hmailserver/hmailserver/-/releases/v6.3.7"
}
],
"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\u0027s 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\u0027s host name or in a hosted domain\u0027s 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\u0027s 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\u0027s 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."
}
],
"title": "Unintended Proxy or Intermediary (\u0027Confused Deputy\u0027) in hMailServer"
}
},
"cveMetadata": {
"assignerOrgId": "ceab7361-8a18-47b1-92ba-4d7d25f6715a",
"assignerShortName": "GitLab",
"cveId": "CVE-2026-114478",
"datePublished": "2026-10-21T15:12:35.847Z",
"dateReserved": "2026-10-21T15:11:45.854Z",
"dateUpdated": "2026-10-29T20:55:51.043Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"epss": {
"cve": "CVE-2026-114478",
"date": "2026-11-04",
"epss": "0.00261",
"percentile": "0.17994"
},
"nvd": {
"cve": {
"affected": [
{
"affectedData": [
{
"defaultStatus": "unaffected",
"product": "hMailServer",
"repo": "https://gitlab.com/hmailserver/hmailserver",
"vendor": "Progressive Robot Ltd",
"versions": [
{
"lessThanOrEqual": "6.3.6",
"status": "affected",
"version": "6.0.0",
"versionType": "semver"
}
]
}
],
"source": "cve@gitlab.com"
}
],
"cveTags": [],
"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\u0027s DMARC policy. When the server sent on a copy of mail that came from outside - an account\u0027s forward, a mail rule\u0027s forward, a Sieve redirect, a list\u0027s 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\u0027s From names, whatever the message\u0027s 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\u0027s own host name; and an envelope sender the message came with at a subdomain of a hosted domain was kept. Where that identity\u0027s SPF record authorises the server, other receivers\u0027 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\u0027s mail to an outside address, and one of: SRS or the envelope rewrite enabled; a list whose bounce address is in the domain\u0027s 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."
}
],
"id": "CVE-2026-114478",
"lastModified": "2026-10-29T21:17:12.313",
"metrics": {
"cvssMetricV31": [
{
"cvssData": {
"attackComplexity": "HIGH",
"attackVector": "NETWORK",
"availabilityImpact": "NONE",
"baseScore": 5.9,
"baseSeverity": "MEDIUM",
"confidentialityImpact": "NONE",
"integrityImpact": "HIGH",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N",
"version": "3.1"
},
"exploitabilityScore": 2.2,
"impactScore": 3.6,
"source": "cve@gitlab.com",
"type": "Secondary"
}
],
"ssvcV203": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"ssvcData": {
"id": "CVE-2026-114478",
"options": [
{
"exploitation": "none"
},
{
"automatable": "no"
},
{
"technicalImpact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-10-29T17:33:39.332121Z",
"version": "2.0.3"
}
}
]
},
"published": "2026-10-21T16:17:35.213",
"references": [
{
"source": "cve@gitlab.com",
"url": "https://gitlab.com/hmailserver/hmailserver/-/releases/v6.3.7"
},
{
"source": "cve@gitlab.com",
"url": "https://gitlab.com/hmailserver/hmailserver/-/work_items/90"
}
],
"sourceIdentifier": "cve@gitlab.com",
"vulnStatus": "Awaiting Analysis",
"weaknesses": [
{
"description": [
{
"lang": "en",
"value": "CWE-441"
}
],
"source": "cve@gitlab.com",
"type": "Secondary"
}
]
}
},
"vulnrichment": {
"containers": {
"adp": [
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2026-114478",
"options": [
{
"Exploitation": "none"
},
{
"Automatable": "no"
},
{
"Technical Impact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-10-29T17:33:39.332121Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-10-29T17:33:41.475Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"product": "hMailServer",
"repo": "https://gitlab.com/hmailserver/hmailserver",
"vendor": "Progressive Robot Ltd",
"versions": [
{
"lessThanOrEqual": "6.3.6",
"status": "affected",
"version": "6.0.0",
"versionType": "semver"
}
]
}
],
"credits": [
{
"lang": "en",
"type": "finder",
"value": "Found in the hMailServer project\u0027s own security review (Progressive Robot Ltd)"
}
],
"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\u0027s DMARC policy. When the server sent on a copy of mail that came from outside - an account\u0027s forward, a mail rule\u0027s forward, a Sieve redirect, a list\u0027s 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\u0027s From names, whatever the message\u0027s 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\u0027s own host name; and an envelope sender the message came with at a subdomain of a hosted domain was kept. Where that identity\u0027s SPF record authorises the server, other receivers\u0027 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\u0027s mail to an outside address, and one of: SRS or the envelope rewrite enabled; a list whose bounce address is in the domain\u0027s 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."
}
],
"metrics": [
{
"cvssV3_1": {
"attackComplexity": "HIGH",
"attackVector": "NETWORK",
"availabilityImpact": "NONE",
"baseScore": 5.9,
"baseSeverity": "MEDIUM",
"confidentialityImpact": "NONE",
"integrityImpact": "HIGH",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N",
"version": "3.1"
},
"format": "CVSS",
"scenarios": [
{
"lang": "en",
"value": "GENERAL"
}
]
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-441",
"description": "CWE-441: Unintended Proxy or Intermediary (\u0027Confused Deputy\u0027)",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-10-21T15:12:35.847Z",
"orgId": "ceab7361-8a18-47b1-92ba-4d7d25f6715a",
"shortName": "GitLab"
},
"references": [
{
"url": "https://gitlab.com/hmailserver/hmailserver/-/work_items/90"
},
{
"url": "https://gitlab.com/hmailserver/hmailserver/-/releases/v6.3.7"
}
],
"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\u0027s 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\u0027s host name or in a hosted domain\u0027s 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\u0027s 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\u0027s 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."
}
],
"title": "Unintended Proxy or Intermediary (\u0027Confused Deputy\u0027) in hMailServer"
}
},
"cveMetadata": {
"assignerOrgId": "ceab7361-8a18-47b1-92ba-4d7d25f6715a",
"assignerShortName": "GitLab",
"cveId": "CVE-2026-114478",
"datePublished": "2026-10-21T15:12:35.847Z",
"dateReserved": "2026-10-21T15:11:45.854Z",
"dateUpdated": "2026-10-29T20:55:51.043Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
Loading…
Loading…
Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.
Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
Vulnerability timeline
Sightings and recorded dates, grouped by day · UTC
Loading timeline…
Loading…
Loading…
The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
Loading…
Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.