cvelistv5 - cve-2026-4339

CVE-2026-4339 (GCVE-0-2026-4339)

Vulnerability from cvelistv5

Published

2026-06-26 14:44

Modified

2026-06-26 15:40

Severity ?

6.5 (Medium) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N

CWE

CWE-918 - Server-Side Request Forgery (SSRF)

Summary

Mattermost versions 10.11.x <= 10.11.18, 11.6.x <= 11.6.3, 11.5.x <= 11.5.6 fail to validate attachment URLs against internal or private IP ranges in the Mattermost Agents plugin MCP server which allows an attacker with access to the MCP server in stdio mode to perform server-side request forgery (SSRF) and exfiltrate data from internal network services via supplying internal URLs as file attachments in post creation requests.. Mattermost Advisory ID: MMSA-2026-00635

References

URL

Tags

https://mattermost.com/security-updates

vendor-advisory

Impacted products

	Vendor	Product	Version
	Mattermost	Mattermost	Version: 10.11.0 ≤ 10.11.18 Version: 11.6.0 ≤ 11.6.3 Version: 11.5.0 ≤ 11.5.6

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-4339",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-06-26T15:40:26.600436Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-06-26T15:40:33.300Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Mattermost",
          "vendor": "Mattermost",
          "versions": [
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              "status": "affected",
              "version": "10.11.0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "11.6.3",
              "status": "affected",
              "version": "11.6.0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "11.5.6",
              "status": "affected",
              "version": "11.5.0",
              "versionType": "semver"
            },
            {
              "status": "unaffected",
              "version": "11.7.0"
            },
            {
              "status": "unaffected",
              "version": "10.11.19"
            },
            {
              "status": "unaffected",
              "version": "11.6.4"
            },
            {
              "status": "unaffected",
              "version": "11.5.7"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "finder",
          "value": "s00me00ne"
        }
      ],
      "descriptions": [
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          "lang": "en",
          "value": "Mattermost versions 10.11.x \u003c= 10.11.18, 11.6.x \u003c= 11.6.3, 11.5.x \u003c= 11.5.6 fail to validate attachment URLs against internal or private IP ranges in the Mattermost Agents plugin MCP server which allows an attacker with access to the MCP server in stdio mode to perform server-side request forgery (SSRF) and exfiltrate data from internal network services via supplying internal URLs as file attachments in post creation requests.. Mattermost Advisory ID: MMSA-2026-00635"
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "LOCAL",
            "availabilityImpact": "NONE",
            "baseScore": 6.5,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "HIGH",
            "integrityImpact": "NONE",
            "privilegesRequired": "LOW",
            "scope": "CHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N",
            "version": "3.1"
          },
          "format": "CVSS",
          "scenarios": [
            {
              "lang": "en",
              "value": "GENERAL"
            }
          ]
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-918",
              "description": "CWE-918: Server-Side Request Forgery (SSRF)",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-06-26T14:44:58.655Z",
        "orgId": "9302f53e-dde5-4bf3-b2f2-a83f91ac0eee",
        "shortName": "Mattermost"
      },
      "references": [
        {
          "name": "MMSA-2026-00635",
          "tags": [
            "vendor-advisory"
          ],
          "url": "https://mattermost.com/security-updates"
        }
      ],
      "solutions": [
        {
          "lang": "en",
          "value": "Update Mattermost to versions 11.7.0, 10.11.19, 11.6.4, 11.5.7 or higher."
        }
      ],
      "source": {
        "advisory": "MMSA-2026-00635",
        "defect": [
          "https://mattermost.atlassian.net/browse/MM-67950"
        ],
        "discovery": "EXTERNAL"
      },
      "title": "SSRF via unvalidated attachment URLs in Mattermost Agents plugin MCP server",
      "x_generator": {
        "engine": "cvelib 1.8.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "9302f53e-dde5-4bf3-b2f2-a83f91ac0eee",
    "assignerShortName": "Mattermost",
    "cveId": "CVE-2026-4339",
    "datePublished": "2026-06-26T14:44:58.655Z",
    "dateReserved": "2026-03-17T14:57:10.575Z",
    "dateUpdated": "2026-06-26T15:40:33.300Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "vulnrichment": {
      "containers": "{\"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-4339\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"no\"}, {\"Technical Impact\": \"partial\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-06-26T15:40:26.600436Z\"}}}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-06-26T15:40:28.917Z\"}}], \"cna\": {\"title\": \"SSRF via unvalidated attachment URLs in Mattermost Agents plugin MCP server\", \"source\": {\"defect\": [\"https://mattermost.atlassian.net/browse/MM-67950\"], \"advisory\": \"MMSA-2026-00635\", \"discovery\": \"EXTERNAL\"}, \"credits\": [{\"lang\": \"en\", \"type\": \"finder\", \"value\": \"s00me00ne\"}], \"metrics\": [{\"format\": \"CVSS\", \"cvssV3_1\": {\"scope\": \"CHANGED\", \"version\": \"3.1\", \"baseScore\": 6.5, \"attackVector\": \"LOCAL\", \"baseSeverity\": \"MEDIUM\", \"vectorString\": \"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N\", \"integrityImpact\": \"NONE\", \"userInteraction\": \"NONE\", \"attackComplexity\": \"LOW\", \"availabilityImpact\": \"NONE\", \"privilegesRequired\": \"LOW\", \"confidentialityImpact\": \"HIGH\"}, \"scenarios\": [{\"lang\": \"en\", \"value\": \"GENERAL\"}]}], \"affected\": [{\"vendor\": \"Mattermost\", \"product\": \"Mattermost\", \"versions\": [{\"status\": \"affected\", \"version\": \"10.11.0\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"10.11.18\"}, {\"status\": \"affected\", \"version\": \"11.6.0\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"11.6.3\"}, {\"status\": \"affected\", \"version\": \"11.5.0\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"11.5.6\"}, {\"status\": \"unaffected\", \"version\": \"11.7.0\"}, {\"status\": \"unaffected\", \"version\": \"10.11.19\"}, {\"status\": \"unaffected\", \"version\": \"11.6.4\"}, {\"status\": \"unaffected\", \"version\": \"11.5.7\"}], \"defaultStatus\": \"unaffected\"}], \"solutions\": [{\"lang\": \"en\", \"value\": \"Update Mattermost to versions 11.7.0, 10.11.19, 11.6.4, 11.5.7 or higher.\"}], \"references\": [{\"url\": \"https://mattermost.com/security-updates\", \"name\": \"MMSA-2026-00635\", \"tags\": [\"vendor-advisory\"]}], \"x_generator\": {\"engine\": \"cvelib 1.8.0\"}, \"descriptions\": [{\"lang\": \"en\", \"value\": \"Mattermost versions 10.11.x \u003c= 10.11.18, 11.6.x \u003c= 11.6.3, 11.5.x \u003c= 11.5.6 fail to validate attachment URLs against internal or private IP ranges in the Mattermost Agents plugin MCP server which allows an attacker with access to the MCP server in stdio mode to perform server-side request forgery (SSRF) and exfiltrate data from internal network services via supplying internal URLs as file attachments in post creation requests.. Mattermost Advisory ID: MMSA-2026-00635\"}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-918\", \"description\": \"CWE-918: Server-Side Request Forgery (SSRF)\"}]}], \"providerMetadata\": {\"orgId\": \"9302f53e-dde5-4bf3-b2f2-a83f91ac0eee\", \"shortName\": \"Mattermost\", \"dateUpdated\": \"2026-06-26T14:44:58.655Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-4339\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-06-26T15:40:33.300Z\", \"dateReserved\": \"2026-03-17T14:57:10.575Z\", \"assignerOrgId\": \"9302f53e-dde5-4bf3-b2f2-a83f91ac0eee\", \"datePublished\": \"2026-06-26T14:44:58.655Z\", \"assignerShortName\": \"Mattermost\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}

CERTFR-2026-AVI-0660

Vulnerability from certfr_avis

De multiples vulnérabilités ont été découvertes dans les produits Mattermost. Elles permettent à un attaquant de provoquer une atteinte à la confidentialité des données, un contournement de la politique de sécurité et un problème de sécurité non spécifié par l'éditeur.

Solutions

Se référer au bulletin de sécurité de l'éditeur pour l'obtention des correctifs (cf. section Documentation).

Impacted products

Vendor	Product	Description
Mattermost	Mattermost Server	Mattermost Server versions 10.11.x antérieures à 10.11.19
Mattermost	Mattermost Server	Mattermost Server versions 11.6.x antérieures à 11.6.4
Mattermost	Mattermost Server	Mattermost Server versions 11.5.x antérieures à 11.5.7

References

Title

Publication Time

Tags

Bulletin de sécurité Mattermost MMSA-2026-00619	2026-05-27	vendor-advisory
Bulletin de sécurité Mattermost MMSA-2026-00635	2026-05-27	vendor-advisory

Show details on source website

JSON

To clipboard

{
  "$ref": "https://www.cert.ssi.gouv.fr/openapi.json",
  "affected_systems": [
    {
      "description": "Mattermost Server versions 10.11.x ant\u00e9rieures \u00e0 10.11.19",
      "product": {
        "name": "Mattermost Server",
        "vendor": {
          "name": "Mattermost",
          "scada": false
        }
      }
    },
    {
      "description": "Mattermost Server versions 11.6.x ant\u00e9rieures \u00e0 11.6.4",
      "product": {
        "name": "Mattermost Server",
        "vendor": {
          "name": "Mattermost",
          "scada": false
        }
      }
    },
    {
      "description": "Mattermost Server versions 11.5.x ant\u00e9rieures \u00e0 11.5.7",
      "product": {
        "name": "Mattermost Server",
        "vendor": {
          "name": "Mattermost",
          "scada": false
        }
      }
    }
  ],
  "affected_systems_content": "",
  "content": "## Solutions\n\nSe r\u00e9f\u00e9rer au bulletin de s\u00e9curit\u00e9 de l\u0027\u00e9diteur pour l\u0027obtention des correctifs (cf. section Documentation).",
  "cves": [
    {
      "name": "CVE-2026-4339",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-4339"
    },
    {
      "name": "CVE-2026-3472",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-3472"
    }
  ],
  "initial_release_date": "2026-05-29T00:00:00",
  "last_revision_date": "2026-08-14T00:00:00",
  "links": [],
  "reference": "CERTFR-2026-AVI-0660",
  "revisions": [
    {
      "description": "Version initiale",
      "revision_date": "2026-05-29T00:00:00.000000"
    },
    {
      "description": "Ajout d\u0027identifiants CVE et modification des risques en cons\u00e9quence.",
      "revision_date": "2026-08-14T00:00:00.000000"
    }
  ],
  "risks": [
    {
      "description": "Non sp\u00e9cifi\u00e9 par l\u0027\u00e9diteur"
    },
    {
      "description": "Contournement de la politique de s\u00e9curit\u00e9"
    },
    {
      "description": "Atteinte \u00e0 la confidentialit\u00e9 des donn\u00e9es"
    }
  ],
  "summary": "De multiples vuln\u00e9rabilit\u00e9s ont \u00e9t\u00e9 d\u00e9couvertes dans les produits Mattermost. Elles permettent \u00e0 un attaquant de provoquer une atteinte \u00e0 la confidentialit\u00e9 des donn\u00e9es, un contournement de la politique de s\u00e9curit\u00e9 et un probl\u00e8me de s\u00e9curit\u00e9 non sp\u00e9cifi\u00e9 par l\u0027\u00e9diteur.",
  "title": "Multiples vuln\u00e9rabilit\u00e9s dans les produits Mattermost",
  "vendor_advisories": [
    {
      "published_at": "2026-05-27",
      "title": "Bulletin de s\u00e9curit\u00e9 Mattermost MMSA-2026-00619",
      "url": "https://mattermost.com/security-updates/"
    },
    {
      "published_at": "2026-05-27",
      "title": "Bulletin de s\u00e9curit\u00e9 Mattermost MMSA-2026-00635",
      "url": "https://mattermost.com/security-updates/"
    }
  ]
}

Sightings

Author	Source	Type	Date

Nomenclature

Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
Confirmed: The vulnerability is confirmed from an analyst perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
Patched: This vulnerability was successfully patched by the user reporting the sighting.
Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
Not confirmed: The user expresses doubt about the veracity of the vulnerability.
Not patched: This vulnerability was not successfully patched by the user reporting the sighting.

Action not permitted

CVE-2026-4339 (GCVE-0-2026-4339)

Vulnerability from cvelistv5

CERTFR-2026-AVI-0660

Vulnerability from certfr_avis

Solutions

Tags

Sightings

Nomenclature