Vulnerability-Lookup

GHSA-R5VF-GRCX-5VQP

Vulnerability from github – Published: 2026-05-26 13:30 – Updated: 2026-05-26 13:30

Details

Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to validate the OAuth token scope on the callback which allows an authenticated Mattermost user to gain access to private repositories via modifying the scope parameter in the GitHub authorization URL.. Mattermost Advisory ID: MMSA-2026-00628

Severity

5.4 (Medium)


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

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{
  "affected": [],
  "aliases": [
    "CVE-2026-28735"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-863"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-05-22T17:16:46Z",
    "severity": "MODERATE"
  },
  "details": "Mattermost versions 11.6.x \u003c= 11.6.0, 11.5.x \u003c= 11.5.3, 11.4.x \u003c= 11.4.4, 10.11.x \u003c= 10.11.14 fail to validate the OAuth token scope on the callback which allows an authenticated Mattermost user to gain access to private repositories via modifying the scope parameter in the GitHub authorization URL.. Mattermost Advisory ID: MMSA-2026-00628",
  "id": "GHSA-r5vf-grcx-5vqp",
  "modified": "2026-05-26T13:30:19Z",
  "published": "2026-05-26T13:30:19Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-28735"
    },
    {
      "type": "WEB",
      "url": "https://mattermost.com/security-updates"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2026-28735 (GCVE-0-2026-28735)

Vulnerability from cvelistv5 – Published: 2026-05-22 16:26 – Updated: 2026-05-22 16:56

Title

GitHub OAuth Scope Validation

Summary

Severity

5.4 (Medium)


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

CWE

CWE-863 - Incorrect Authorization

Assigner

Mattermost

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 , ≤ 11.6.0 (semver) Affected: 11.5.0 , ≤ 11.5.3 (semver) Affected: 11.4.0 , ≤ 11.4.4 (semver) Affected: 10.11.0 , ≤ 10.11.14 (semver) Unaffected: 11.7.0 Unaffected: 11.6.1 Unaffected: 11.5.4 Unaffected: 11.4.5 Unaffected: 10.11.15

Credits

eahmed

Show details on NVD website

JSON

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{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-28735",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-05-22T16:55:25.541191Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-05-22T16:56:09.671Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Mattermost",
          "vendor": "Mattermost",
          "versions": [
            {
              "lessThanOrEqual": "11.6.0",
              "status": "affected",
              "version": "11.6.0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "11.5.3",
              "status": "affected",
              "version": "11.5.0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "11.4.4",
              "status": "affected",
              "version": "11.4.0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "10.11.14",
              "status": "affected",
              "version": "10.11.0",
              "versionType": "semver"
            },
            {
              "status": "unaffected",
              "version": "11.7.0"
            },
            {
              "status": "unaffected",
              "version": "11.6.1"
            },
            {
              "status": "unaffected",
              "version": "11.5.4"
            },
            {
              "status": "unaffected",
              "version": "11.4.5"
            },
            {
              "status": "unaffected",
              "version": "10.11.15"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "finder",
          "value": "eahmed"
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "Mattermost versions 11.6.x \u003c= 11.6.0, 11.5.x \u003c= 11.5.3, 11.4.x \u003c= 11.4.4, 10.11.x \u003c= 10.11.14 fail to validate the OAuth token scope on the callback which allows an authenticated Mattermost user to gain access to private repositories via modifying the scope parameter in the GitHub authorization URL.. Mattermost Advisory ID: MMSA-2026-00628"
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "NONE",
            "baseScore": 5.4,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "LOW",
            "integrityImpact": "LOW",
            "privilegesRequired": "LOW",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N",
            "version": "3.1"
          },
          "format": "CVSS",
          "scenarios": [
            {
              "lang": "en",
              "value": "GENERAL"
            }
          ]
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-863",
              "description": "CWE-863: Incorrect Authorization",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-05-22T16:26:04.066Z",
        "orgId": "9302f53e-dde5-4bf3-b2f2-a83f91ac0eee",
        "shortName": "Mattermost"
      },
      "references": [
        {
          "name": "MMSA-2026-00628",
          "tags": [
            "vendor-advisory"
          ],
          "url": "https://mattermost.com/security-updates"
        }
      ],
      "solutions": [
        {
          "lang": "en",
          "value": "Update Mattermost to versions 11.7.0, 11.6.1, 11.5.4, 11.4.5, 10.11.15 or higher."
        }
      ],
      "source": {
        "advisory": "MMSA-2026-00628",
        "defect": [
          "https://mattermost.atlassian.net/browse/MM-67857"
        ],
        "discovery": "EXTERNAL"
      },
      "title": "GitHub OAuth Scope Validation"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "9302f53e-dde5-4bf3-b2f2-a83f91ac0eee",
    "assignerShortName": "Mattermost",
    "cveId": "CVE-2026-28735",
    "datePublished": "2026-05-22T16:26:04.066Z",
    "dateReserved": "2026-03-10T13:45:39.998Z",
    "dateUpdated": "2026-05-22T16:56:09.671Z",
    "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.

Action not permitted

GHSA-R5VF-GRCX-5VQP

CVE-2026-28735 (GCVE-0-2026-28735)

Tags

Sightings

Nomenclature