CVE-2026-3433Network attack vector

Private-team role disclosure via global WebSocket broadcasts

Published Jun 12, 2026 · Updated Jun 12, 2026

Information disclosure in Mattermost allows remote authenticated users with guest access to view private-team role change notifications. The server broadcasts role_updated WebSocket events globally instead of setting the affected team or channel in each event's broadcast scope. Guest-level access and a WebSocket connection suffice in 10.11.0 through 10.11.16, 11.5.0 through 11.5.4, and 11.6.0 through 11.6.1; the reported consequence is limited to notification disclosure.

CVSS severity4.3
Medium
EPSS probability0.18%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Information disclosure in Mattermost allows remote authenticated users with guest access to view private-team role change notifications. The server broadcasts role_updated WebSocket events globally instead of setting the affected team or channel in each event's broadcast scope. Guest-level access and a WebSocket connection suffice in 10.11.0 through 10.11.16, 11.5.0 through 11.5.4, and 11.6.0 through 11.6.1; the reported consequence is limited to notification disclosure.

The record

CVE
CVE-2026-3433
Published
Jun 12, 2026
Updated
Jun 12, 2026
Vendor
Mattermost
Product
Mattermost
Classifications
CWE-200, T1213.005
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jun 12, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 12, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=10.11.0 <=10.11.15
  2. Affected versionversion=10.11.0 <=10.11.16
  3. Affected versionversion=11.5.0 <=11.5.4
  4. Affected versionversion=11.6.0 <=11.6.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Mattermost · Mattermostversion=10.11.0 <=10.11.15; version=10.11.0 <=10.11.16; version=11.5.0 <=11.5.4; version=11.6.0 <=11.6.1

Published CVSS scores

4.3Mattermost, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-200Exposure of Sensitive Information to an Unauthorized Actor
T1213.005Data from Information Repositories: Messaging Applications

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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