CVE-2026-107587

Status: DeferredMedium (5.9)—

Improper certificate validation in the webmail of Progressive Robot hMailServer 6.3.2 through 6.3.5 allows a remote unauthenticated attacker to have S/MIME-encrypted mail that the account later sends to another correspondent also encrypted to the attacker's key. When its recipient opened a signed message, the webmail kept the signer's certificate for encrypting replies whether or not the server found its chain trusted, under the first e-mail address the certificate listed rather than the message's From address, and beside any certificate already held for that address. Encrypted mail later sent from the webmail to that address was encrypted to every certificate held for it, so a holder of the kept certificate's key who obtains a copy of such a message can read it.

CVSS

Version: 3.1
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:L/A:N
Base score: 5.9

Exploitation probability (EPSS)

Probability of exploitation in the next 30 days: 0.17%
Percentile among all scored CVEs: 6
Score date: 10/13/2026

EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).

🎯 ATT&CK techniques

How this vulnerability is exploited and what the attacker gains, in MITRE ATT&CK terms.

ExploitationT1203 Exploitation for Client Executionexecution85 %
Primary impactT1557 Adversary-in-the-Middlecredential access · collection80 %
Secondary impactT1005 Data from Local Systemcollection75 %

UI:R (interacción del usuario al abrir mensaje firmado) → T1203. MITM capaz de interceptar correo cifrado a su clave (T1557) y leer contenido (C:H) → T1005 como impacto secundario. CWE-295 valida el vector.

Inferred by our analysis agent from the official description, CVSS vector and CWE, and checked by a supervisor. May contain errors.

🛡️ ATT&CK mitigations that cover these techniques

User Training Network Segmentation Network Intrusion Prevention Limit Access to Resource Over Network Filter Network Traffic Encrypt Sensitive Information

Affected technologies (1)

⚠ AI-inferred from the description — NVD hasn't analyzed this CVE yet, these aren't verified CPEs.

Hmailserver — Hmailserver^AI

CWEs

CWE-295

References

Raw JSON (NVD)

Show

{
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  "metrics": {
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          "options": [
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          "version": "2.0.3",
          "timestamp": "2026-10-08T14:13:29.336107Z"
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          "integrityImpact": "LOW",
          "userInteraction": "REQUIRED",
          "attackComplexity": "HIGH",
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          "privilegesRequired": "NONE",
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      "affectedData": [
        {
          "repo": "https://gitlab.com/hmailserver/hmailserver",
          "vendor": "Progressive Robot Ltd",
          "product": "hMailServer",
          "versions": [
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              "status": "affected",
              "version": "6.3.2",
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  "published": "2026-10-08T12:17:16.937",
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    }
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  "lastModified": "2026-10-08T21:02:43.860",
  "sourceIdentifier": "cve@gitlab.com"
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