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CVE-2026-3433

Mattermost fails to scope role_updated websocket events to authorized team and channel members

CVSS 3.1 4.3 MEDIUMEUVD CVSS 3.1 4.3 CVSS 3.1 · [email protected] · Secondary 4.3 MEDIUMCVSS_V3 Publisher rating MODERATEFixed by github.com/mattermost/mattermost-server 11.6.1Fixed by github.com/mattermost/mattermost-server 11.5.5Fixed by github.com/mattermost/mattermost-server 10.11.17Fixed by github.com/mattermost/mattermost/server/v8 8.0.0-20260504071740-9408b98025d7osv · severity unknownFixed by github.com/mattermost/mattermost-server 10.11.17+incompatibleFixed by github.com/mattermost/mattermost-server 11.5.5+incompatibleFixed by github.com/mattermost/mattermost-server 11.6.1+incompatibleFixed by github.com/mattermost/mattermost/server/v8 8.0.0-20260504071740-9408b98025d7KEV status unknown
Original advisory

cve-program · CVE-2026-3433

Published

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 restrict role_updated websocket event broadcasts to members of the affected team or channel which allows an authenticated attacker with guest-level access to observe permission scheme change notifications for private teams they are not a member of via the websocket connection.. Mattermost Advisory ID: MMSA-2026-00616

Read the publisher's advisory

euvd · EUVD-2026-36498

Published

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 restrict role_updated websocket event broadcasts to members of the affected team or channel which allows an authenticated attacker with guest-level access to observe permission scheme change notifications for private teams they are not a member of via the websocket connection.. Mattermost Advisory ID: MMSA-2026-00616

Read the publisher's advisory

nvd · CVE-2026-3433

Published

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 restrict role_updated websocket event broadcasts to members of the affected team or channel which allows an authenticated attacker with guest-level access to observe permission scheme change notifications for private teams they are not a member of via the websocket connection.. Mattermost Advisory ID: MMSA-2026-00616

Read the publisher's advisory

osv · GHSA-rp4v-qc77-phm4

Published

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 restrict role_updated websocket event broadcasts to members of the affected team or channel, which allows an authenticated attacker with guest-level access to observe permission scheme change notifications for private teams they are not a member of via the websocket connection. Mattermost Advisory ID: MMSA-2026-00616

Read the publisher's advisory

osv · GO-2026-6286

Published

Mattermost doesn't restrict role_updated websocket event broadcasts to members of the affected team or channel in github.com/mattermost/mattermost-server

Read the publisher's advisory

Affected versions, risk and source history

cve-program · CVE-2026-3433

Published

Mattermost

Vendor product

Publisher's version information

Shown as published. These rules are not interpreted as NuGet package version ranges.

{
                    "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"
                        },
                        {
                            "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",
                            "status": "unaffected"
                        }
                    ]
                }

Original source record · Cite this exact observation · Complete original publisher JSON

euvd · EUVD-2026-36498

Published

EUVD source date text has no stated timezone and is retained without inventing a UTC instant. Related bulletin membership is not an alias, common cause or applicability claim. A missing vector with a zero score is treated as unrated. Complete vendor/product and underlying source evidence remains in the original JSON.

Original publisher date fields

datePublished: Jun 12, 2026, 3:46:54 PM

dateUpdated: Jun 12, 2026, 5:19:49 PM

1 related source bulletins · separate from aliases

WID-SEC-W-2026-1529: Mattermost Server: Mehrere Schwachstellen ermöglichen nicht spezifizierten Angriff

CVE-2026-3433 · CVE-2026-6046 · CVE-2026-6689 · CVE-2026-6739 · CVE-2026-6961 · CVE-2026-7387

No normalized affected-package data is projected for this source revision. The original publisher record may contain additional product and version evidence; this does not establish that a package is unaffected.

Original source record · Cite this exact observation · Complete original publisher JSON

nvd · CVE-2026-3433

Published

NVD analysis and CPE criteria are source context, not proof that a package or your environment is affected. Complete affected data, logical configurations and SSVC are retained in the original JSON.

Source analysis status: Analyzed

Weakness classifications: CWE-200

Original publisher date fields

published: 2026-06-12T17:16:22.467

lastModified: 2026-06-18T14:31:31.480

1 source CPE criteria · context only
  • cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*

The original JSON retains the logical configuration operators, exclusions and version bounds.

No normalized affected-package data is projected for this source revision. The original publisher record may contain additional product and version evidence; this does not establish that a package is unaffected.

Original source record · Cite this exact observation · Complete original publisher JSON

osv · GHSA-rp4v-qc77-phm4

Published

github.com/mattermost/mattermost-server

Go

SEMVER · introduced 11.6.0 → fixed 11.6.1

1 versions listed as affected

11.6.0

github.com/mattermost/mattermost-server

Go

SEMVER · introduced 11.5.0 → fixed 11.5.5

github.com/mattermost/mattermost-server

Go

SEMVER · introduced 10.11.0 → fixed 10.11.17

github.com/mattermost/mattermost/server/v8

Go

SEMVER · introduced 8.0.0-20250731163400-5b955468ea1e → fixed 8.0.0-20260504071740-9408b98025d7

Original source record · Cite this exact observation · Complete original publisher JSON

osv · GO-2026-6286

Published

github.com/mattermost/mattermost-server

Go

SEMVER · introduced 10.11.0+incompatible → fixed 10.11.17+incompatible → introduced 11.5.0+incompatible → fixed 11.5.5+incompatible → introduced 11.6.0+incompatible → fixed 11.6.1+incompatible

github.com/mattermost/mattermost-server/v5

Go

SEMVER · introduced 0

github.com/mattermost/mattermost-server/v6

Go

SEMVER · introduced 0

github.com/mattermost/mattermost/server/v8

Go

SEMVER · introduced 8.0.0-20250731163400-5b955468ea1e → fixed 8.0.0-20260504071740-9408b98025d7

Original source record · Cite this exact observation · Complete original publisher JSON

ChangeIntel

An IT change radar: releases, security, known issues, retirements, documentation changes, and service status from public sources. Every item links to supporting evidence; dates and statuses can change after they are read.

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