Vulnerability-Lookup

CVE-2026-4646 (GCVE-0-2026-4646)

Vulnerability from cvelistv5 – Published: 2026-05-22 10:25 – Updated: 2026-05-22 12:13

Title

Insufficient input validation in GitHub plugin API causes denial of service

Summary

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 user-supplied input in API request handlers which allows an authenticated attacker to crash the plugin process via a crafted HTTP request to the PR details endpoint.. Mattermost Advisory ID: MMSA-2026-00638

Severity

4.3 (Medium)


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

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-05-22 12:13 UTC

CWE

CWE-1287 - Improper Validation of Specified Type of Input

Assigner

Mattermost mitre root

References

1 reference

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

Impacted products

1 product

Vendor	Product	Version	CPE status
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	guessed

Credits

Mariusz Maik

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-4646

Vulnerability from fkie_nvd - Published: 2026-05-22 11:16 - Updated: 2026-07-23 16:10

Severity

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

Summary

References

	URL	Tags
	responsibledisclosure@mattermost.com	https://mattermost.com/security-updates	Vendor Advisory

Impacted products

Vendor	Product	Version
mattermost	mattermost_server	*
mattermost	mattermost_server	*
mattermost	mattermost_server	*
mattermost	mattermost_server	*

JSON

To clipboard

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}

GHSA-RMVV-8V8W-RF7X

Vulnerability from github – Published: 2026-05-26 13:30 – Updated: 2026-06-29 19:21

Summary

Mattermost doesn't validate user-supplied input in API request handlers

Details

Severity

4.3 (Medium)


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

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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"
      ]
    },
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/mattermost/mattermost-server"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "11.5.0"
            },
            {
              "fixed": "11.5.4"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/mattermost/mattermost-server"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "11.4.0"
            },
            {
              "fixed": "11.4.5"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/mattermost/mattermost-server"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "10.11.0"
            },
            {
              "fixed": "10.11.15"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/mattermost/mattermost-plugin-github"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.0.1-0.20260330164815-c2840e980b3c"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-4646"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-1287"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-06-29T19:21:37Z",
    "nvd_published_at": "2026-05-22T11:16:22Z",
    "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 user-supplied input in API request handlers which allows an authenticated attacker to crash the plugin process via a crafted HTTP request to the PR details endpoint. Mattermost Advisory ID: MMSA-2026-00638",
  "id": "GHSA-rmvv-8v8w-rf7x",
  "modified": "2026-06-29T19:21:37Z",
  "published": "2026-05-26T13:30:15Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-4646"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mattermost/mattermost-plugin-github/commit/c2840e980b3c2bd08db656eaa6a0fe26bcbf4695"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/mattermost/mattermost"
    },
    {
      "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:N/I:N/A:L",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Mattermost doesn\u0027t validate user-supplied input in API request handlers"
}

WID-SEC-W-2026-1173

Vulnerability from csaf_certbund - Published: 2026-04-19 22:00 - Updated: 2026-05-25 22:00

Summary

Mattermost: Mehrere Schwachstellen ermöglichen nicht spezifizierten Angriff

Severity

Mittel

Scope

3 vulnerabilities in this advisory, including CVE-2026-4646.

CVE-2026-4646

Known affected: 5 products

Open the full advisory

WID-SEC-W-2026-1243

Vulnerability from csaf_certbund - Published: 2026-04-22 22:00 - Updated: 2026-05-25 22:00

Summary

Mattermost: Mehrere Schwachstellen ermöglichen nicht spezifizierten Angriff

Severity

Mittel

Scope

6 vulnerabilities in this advisory, including CVE-2026-4646.

CVE-2026-4646

Known affected: 5 products

Open the full advisory

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.
Browse all ATT&CK techniques and the vulnerabilities related to each.

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.

Action not permitted

CVE-2026-4646 (GCVE-0-2026-4646)

FKIE_CVE-2026-4646

GHSA-RMVV-8V8W-RF7X

WID-SEC-W-2026-1173

WID-SEC-W-2026-1243

Tags

Sightings

Nomenclature

Related by attack behaviour