CVE-2026-107587 (GCVE-0-2026-107587)

Vulnerability from cvelistv5 – Published: 2026-10-08 11:49 – Updated: 2026-10-08 14:13
VLAI
Title
Improper Certificate Validation in hMailServer
Summary
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.
Severity
5.9 (Medium)
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:L/A:N
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-10-08 14:13 UTC
CWE
  • CWE-295 - Improper Certificate Validation
Assigner
GitLab CNA under the mitre root
CNA scorecard C 75/100 over 288 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Progressive Robot Ltd hMailServer Affected: 6.3.2 , < 6.3.6 (semver)
guessed Create a notification for this product.
Credits
Found in the hMailServer project's own security review (Progressive Robot Ltd)
Show details on NVD website
To clipboard 

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-107587",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-10-08T14:13:29.336107Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-10-08T14:13:38.084Z",
          "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": [
            {
              "lessThan": "6.3.6",
              "status": "affected",
              "version": "6.3.2",
              "versionType": "semver"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "finder",
          "value": "Found in the hMailServer project\u0027s own security review (Progressive Robot Ltd)"
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "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\u0027s key. When its recipient opened a signed message, the webmail kept the signer\u0027s 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\u0027s 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\u0027s key who obtains a copy of such a message can read it."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "HIGH",
            "attackVector": "NETWORK",
            "availabilityImpact": "NONE",
            "baseScore": 5.9,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "HIGH",
            "integrityImpact": "LOW",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "REQUIRED",
            "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:L/A:N",
            "version": "3.1"
          },
          "format": "CVSS",
          "scenarios": [
            {
              "lang": "en",
              "value": "GENERAL"
            }
          ]
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-295",
              "description": "CWE-295: Improper Certificate Validation",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-08T11:49:01.081Z",
        "orgId": "ceab7361-8a18-47b1-92ba-4d7d25f6715a",
        "shortName": "GitLab"
      },
      "references": [
        {
          "url": "https://gitlab.com/hmailserver/hmailserver/-/work_items/66"
        },
        {
          "url": "https://gitlab.com/hmailserver/hmailserver/-/releases/v6.3.6"
        }
      ],
      "solutions": [
        {
          "lang": "en",
          "value": "Upgrade to hMailServer 6.3.6, whose webmail keeps a signer\u0027s certificate only when its chain is trusted, only under the From address the signature was verified for, and a different certificate for an address that has one only when the reader chooses to. After upgrading, review the correspondents\u0027 certificates on the webmail\u0027s Security page and remove any that should not be there. Until then: check the certificates listed for an address before sending it encrypted mail from the webmail, or encrypt in a mail program."
        }
      ],
      "title": "Improper Certificate Validation in hMailServer"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "ceab7361-8a18-47b1-92ba-4d7d25f6715a",
    "assignerShortName": "GitLab",
    "cveId": "CVE-2026-107587",
    "datePublished": "2026-10-08T11:49:01.081Z",
    "dateReserved": "2026-10-08T11:17:47.802Z",
    "dateUpdated": "2026-10-08T14:13:38.084Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-107587",
      "date": "2026-10-10",
      "epss": "0.00169",
      "percentile": "0.05756"
    },
    "nvd": {
      "cve": {
        "affected": [
          {
            "affectedData": [
              {
                "defaultStatus": "unaffected",
                "product": "hMailServer",
                "repo": "https://gitlab.com/hmailserver/hmailserver",
                "vendor": "Progressive Robot Ltd",
                "versions": [
                  {
                    "lessThan": "6.3.6",
                    "status": "affected",
                    "version": "6.3.2",
                    "versionType": "semver"
                  }
                ]
              }
            ],
            "source": "cve@gitlab.com"
          }
        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "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\u0027s key. When its recipient opened a signed message, the webmail kept the signer\u0027s 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\u0027s 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\u0027s key who obtains a copy of such a message can read it."
          }
        ],
        "id": "CVE-2026-107587",
        "lastModified": "2026-10-08T21:02:43.860",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "HIGH",
                "attackVector": "NETWORK",
                "availabilityImpact": "NONE",
                "baseScore": 5.9,
                "baseSeverity": "MEDIUM",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "LOW",
                "privilegesRequired": "NONE",
                "scope": "UNCHANGED",
                "userInteraction": "REQUIRED",
                "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:L/A:N",
                "version": "3.1"
              },
              "exploitabilityScore": 1.6,
              "impactScore": 4.2,
              "source": "cve@gitlab.com",
              "type": "Secondary"
            }
          ],
          "ssvcV203": [
            {
              "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
              "ssvcData": {
                "id": "CVE-2026-107587",
                "options": [
                  {
                    "exploitation": "none"
                  },
                  {
                    "automatable": "no"
                  },
                  {
                    "technicalImpact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-10-08T14:13:29.336107Z",
                "version": "2.0.3"
              }
            }
          ]
        },
        "published": "2026-10-08T12:17:16.937",
        "references": [
          {
            "source": "cve@gitlab.com",
            "url": "https://gitlab.com/hmailserver/hmailserver/-/releases/v6.3.6"
          },
          {
            "source": "cve@gitlab.com",
            "url": "https://gitlab.com/hmailserver/hmailserver/-/work_items/66"
          }
        ],
        "sourceIdentifier": "cve@gitlab.com",
        "vulnStatus": "Deferred",
        "weaknesses": [
          {
            "description": [
              {
                "lang": "en",
                "value": "CWE-295"
              }
            ],
            "source": "cve@gitlab.com",
            "type": "Secondary"
          }
        ]
      }
    },
    "vulnrichment": {
      "containers": {
        "adp": [
          {
            "metrics": [
              {
                "other": {
                  "content": {
                    "id": "CVE-2026-107587",
                    "options": [
                      {
                        "Exploitation": "none"
                      },
                      {
                        "Automatable": "no"
                      },
                      {
                        "Technical Impact": "partial"
                      }
                    ],
                    "role": "CISA Coordinator",
                    "timestamp": "2026-10-08T14:13:29.336107Z",
                    "version": "2.0.3"
                  },
                  "type": "ssvc"
                }
              }
            ],
            "providerMetadata": {
              "dateUpdated": "2026-10-08T14:13:35.095Z",
              "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": [
                {
                  "lessThan": "6.3.6",
                  "status": "affected",
                  "version": "6.3.2",
                  "versionType": "semver"
                }
              ]
            }
          ],
          "credits": [
            {
              "lang": "en",
              "type": "finder",
              "value": "Found in the hMailServer project\u0027s own security review (Progressive Robot Ltd)"
            }
          ],
          "descriptions": [
            {
              "lang": "en",
              "value": "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\u0027s key. When its recipient opened a signed message, the webmail kept the signer\u0027s 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\u0027s 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\u0027s key who obtains a copy of such a message can read it."
            }
          ],
          "metrics": [
            {
              "cvssV3_1": {
                "attackComplexity": "HIGH",
                "attackVector": "NETWORK",
                "availabilityImpact": "NONE",
                "baseScore": 5.9,
                "baseSeverity": "MEDIUM",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "LOW",
                "privilegesRequired": "NONE",
                "scope": "UNCHANGED",
                "userInteraction": "REQUIRED",
                "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:L/A:N",
                "version": "3.1"
              },
              "format": "CVSS",
              "scenarios": [
                {
                  "lang": "en",
                  "value": "GENERAL"
                }
              ]
            }
          ],
          "problemTypes": [
            {
              "descriptions": [
                {
                  "cweId": "CWE-295",
                  "description": "CWE-295: Improper Certificate Validation",
                  "lang": "en",
                  "type": "CWE"
                }
              ]
            }
          ],
          "providerMetadata": {
            "dateUpdated": "2026-10-08T11:49:01.081Z",
            "orgId": "ceab7361-8a18-47b1-92ba-4d7d25f6715a",
            "shortName": "GitLab"
          },
          "references": [
            {
              "url": "https://gitlab.com/hmailserver/hmailserver/-/work_items/66"
            },
            {
              "url": "https://gitlab.com/hmailserver/hmailserver/-/releases/v6.3.6"
            }
          ],
          "solutions": [
            {
              "lang": "en",
              "value": "Upgrade to hMailServer 6.3.6, whose webmail keeps a signer\u0027s certificate only when its chain is trusted, only under the From address the signature was verified for, and a different certificate for an address that has one only when the reader chooses to. After upgrading, review the correspondents\u0027 certificates on the webmail\u0027s Security page and remove any that should not be there. Until then: check the certificates listed for an address before sending it encrypted mail from the webmail, or encrypt in a mail program."
            }
          ],
          "title": "Improper Certificate Validation in hMailServer"
        }
      },
      "cveMetadata": {
        "assignerOrgId": "ceab7361-8a18-47b1-92ba-4d7d25f6715a",
        "assignerShortName": "GitLab",
        "cveId": "CVE-2026-107587",
        "datePublished": "2026-10-08T11:49:01.081Z",
        "dateReserved": "2026-10-08T11:17:47.802Z",
        "dateUpdated": "2026-10-08T14:13:38.084Z",
        "state": "PUBLISHED"
      },
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.





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.



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.