Vulnerability-Lookup

GHSA-3VMP-WHVV-5V9V

Vulnerability from github – Published: 2026-06-12 18:31 – Updated: 2026-08-24 21:39

Summary

Mattermost doesn't validate that a username returned during bot registration belongs to a bot account

Details

Mattermost versions 11.6.x <= 11.6.1, 11.5.x <= 11.5.4, 10.11.x <= 10.11.15, 10.11.x <= 10.11.16 fail to validate that a username returned during bot registration belongs to a bot account, which allows an unprivileged attacker to intercept private messages sent by plugins via direct message channels by pre-registering a user account with a predictable plugin bot username. Mattermost Advisory ID: MMSA-2026-00649

Severity

5.3 (Medium)


                  
                    CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N

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{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/mattermost/mattermost-server"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "11.6.0"
            },
            {
              "fixed": "11.6.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "11.6.0"
      ]
    },
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 11.5.4"
      },
      "package": {
        "ecosystem": "Go",
        "name": "github.com/mattermost/mattermost-server"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "11.5.0"
            },
            {
              "fixed": "11.5.5"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 10.11.15"
      },
      "package": {
        "ecosystem": "Go",
        "name": "github.com/mattermost/mattermost-server"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "10.11.0"
            },
            {
              "fixed": "10.11.17"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/mattermost/mattermost/server/v8"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "8.0.0-20250731163400-5b955468ea1e"
            },
            {
              "fixed": "8.0.0-20260428151657-c79c3831061a"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-6046"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-200"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-08-24T21:39:13Z",
    "nvd_published_at": "2026-06-12T17:16:26Z",
    "severity": "MODERATE"
  },
  "details": "Mattermost versions 11.6.x \u003c= 11.6.1, 11.5.x \u003c= 11.5.4, 10.11.x \u003c= 10.11.15, 10.11.x \u003c= 10.11.16 fail to validate that a username returned during bot registration belongs to a bot account, which allows an unprivileged attacker to intercept private messages sent by plugins via direct message channels by pre-registering a user account with a predictable plugin bot username. Mattermost Advisory ID: MMSA-2026-00649",
  "id": "GHSA-3vmp-whvv-5v9v",
  "modified": "2026-08-24T21:39:54Z",
  "published": "2026-06-12T18:31:59Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-6046"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mattermost/mattermost/pull/36320"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mattermost/mattermost/pull/36318"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mattermost/mattermost/pull/36317"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mattermost/mattermost/pull/36305"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mattermost/mattermost/pull/36064"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mattermost/mattermost/commit/f706d1f01e6dfe62cab86c1d257f237daa78106a"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mattermost/mattermost/commit/c79c3831061a0880c0962c7d567c9e24dd35f44c"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mattermost/mattermost/commit/aba9339a24d4b287edd77377c19901d6e341bb96"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mattermost/mattermost/commit/98f9778cec1e7f3d97b3d4692fb91f8e7b659972"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mattermost/mattermost/commit/3be10297c14d272f273d747af70728f9d03c60ec"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mattermost/mattermost/releases/tag/v10.11.16"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mattermost/mattermost/releases/tag/v11.5.5"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mattermost/mattermost/releases/tag/v11.6.2"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mattermost/mattermost/releases/tag/v11.7.0"
    },
    {
      "type": "WEB",
      "url": "https://mattermost.com/security-updates"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/mattermost/mattermost"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Mattermost doesn\u0027t validate that a username returned during bot registration belongs to a bot account"
}

CVE-2026-6046 (GCVE-0-2026-6046)

Vulnerability from cvelistv5 – Published: 2026-06-12 15:52 – Updated: 2026-06-12 17:18

Title

Plugin bot username conflict allows user account to be used as bot identity in Mattermost Server

Summary

Severity

5.3 (Medium)


                        
                          CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-06-12 17:18 UTC

CWE

CWE-200 - Exposure of Sensitive Information to an Unauthorized Actor

Assigner

Mattermost mitre root

References

1 reference

URL	Tags
https://mattermost.com/security-updates	vendor-advisory

Impacted products

1 product

Vendor	Product	Version
Mattermost	Mattermost	Affected: 11.6.0 , ≤ 11.6.1 (semver) Affected: 11.5.0 , ≤ 11.5.4 (semver) Affected: 10.11.0 , ≤ 10.11.15 (semver) Affected: 10.11.0 , ≤ 10.11.16 (semver) Unaffected: 11.7.0 Unaffected: 11.6.2 Unaffected: 11.5.5 Unaffected: 10.11.16 Unaffected: 10.11.17

Credits

insomnia1102

Show details on NVD website

JSON

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{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-6046",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-06-12T17:18:25.567701Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-06-12T17:18:30.553Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Mattermost",
          "vendor": "Mattermost",
          "versions": [
            {
              "lessThanOrEqual": "11.6.1",
              "status": "affected",
              "version": "11.6.0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "11.5.4",
              "status": "affected",
              "version": "11.5.0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "10.11.15",
              "status": "affected",
              "version": "10.11.0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "10.11.16",
              "status": "affected",
              "version": "10.11.0",
              "versionType": "semver"
            },
            {
              "status": "unaffected",
              "version": "11.7.0"
            },
            {
              "status": "unaffected",
              "version": "11.6.2"
            },
            {
              "status": "unaffected",
              "version": "11.5.5"
            },
            {
              "status": "unaffected",
              "version": "10.11.16"
            },
            {
              "status": "unaffected",
              "version": "10.11.17"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "finder",
          "value": "insomnia1102"
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "Mattermost versions 11.6.x \u003c= 11.6.1, 11.5.x \u003c= 11.5.4, 10.11.x \u003c= 10.11.15, 10.11.x \u003c= 10.11.16 fail to validate that a username returned during bot registration belongs to a bot account, which allows an unprivileged attacker to intercept private messages sent by plugins via direct message channels by pre-registering a user account with a predictable plugin bot username.. Mattermost Advisory ID: MMSA-2026-00649"
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "HIGH",
            "attackVector": "NETWORK",
            "availabilityImpact": "NONE",
            "baseScore": 5.3,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "HIGH",
            "integrityImpact": "NONE",
            "privilegesRequired": "LOW",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N",
            "version": "3.1"
          },
          "format": "CVSS",
          "scenarios": [
            {
              "lang": "en",
              "value": "GENERAL"
            }
          ]
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-200",
              "description": "CWE-200 Exposure of Sensitive Information to an Unauthorized Actor",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-06-12T15:52:33.505Z",
        "orgId": "9302f53e-dde5-4bf3-b2f2-a83f91ac0eee",
        "shortName": "Mattermost"
      },
      "references": [
        {
          "name": "MMSA-2026-00649",
          "tags": [
            "vendor-advisory"
          ],
          "url": "https://mattermost.com/security-updates"
        }
      ],
      "solutions": [
        {
          "lang": "en",
          "value": "Update Mattermost to versions 11.7.0, 11.6.2, 11.5.5, 10.11.16, 10.11.17 or higher."
        }
      ],
      "source": {
        "advisory": "MMSA-2026-00649",
        "defect": [
          "https://mattermost.atlassian.net/browse/MM-68256"
        ],
        "discovery": "EXTERNAL"
      },
      "title": "Plugin bot username conflict allows user account to be used as bot identity in Mattermost Server",
      "x_generator": {
        "engine": "cvelib 1.8.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "9302f53e-dde5-4bf3-b2f2-a83f91ac0eee",
    "assignerShortName": "Mattermost",
    "cveId": "CVE-2026-6046",
    "datePublished": "2026-06-12T15:52:33.505Z",
    "dateReserved": "2026-04-09T19:20:26.868Z",
    "dateUpdated": "2026-06-12T17:18:30.553Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

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.

Detection rules are retrieved from Rulezet.

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.

Action not permitted

GHSA-3VMP-WHVV-5V9V

CVE-2026-6046 (GCVE-0-2026-6046)

Tags

Sightings

Nomenclature