CVE-2026-5139Network attack vector

Global integration configuration overwrite via unchecked command

Published Jun 22, 2026 · Updated Jun 22, 2026

Missing authorization in affected Mattermost 10.11, 11.5, 11.6, and 11.7 releases allows remote authenticated users to alter GitLab settings. The /gitlab connect command handler calls setDefaultInstance without verifying that the caller is a system administrator, allowing a supplied instance name to replace the global default. Affected releases are Mattermost 10.11.0 through 10.11.17, 11.5.0 through 11.5.5, 11.6.0 through 11.6.2, and 11.7.0; any authenticated account can disrupt integration behavior without directly reading data.

CVSS severity5.4
Medium
EPSS probability0.29%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Missing authorization in affected Mattermost 10.11, 11.5, 11.6, and 11.7 releases allows remote authenticated users to alter GitLab settings. The /gitlab connect command handler calls setDefaultInstance without verifying that the caller is a system administrator, allowing a supplied instance name to replace the global default. Affected releases are Mattermost 10.11.0 through 10.11.17, 11.5.0 through 11.5.5, 11.6.0 through 11.6.2, and 11.7.0; any authenticated account can disrupt integration behavior without directly reading data.

The record

CVE
CVE-2026-5139
Published
Jun 22, 2026
Updated
Jun 22, 2026
Vendor
Mattermost
Product
Mattermost
Classifications
CWE-862, T1190
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jun 22, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 22, 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 <=10.11.17
  2. Affected versionversion=11.5.0 <=11.5.5
  3. Affected versionversion=11.6.0 <=11.6.2
  4. Affected versionversion=11.7.0 <=11.7.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Mattermost · Mattermostversion=10.11.0 <=10.11.17; version=11.5.0 <=11.5.5; version=11.6.0 <=11.6.2; version=11.7.0 <=11.7.0

Published CVSS scores

5.4Mattermost, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L

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-862Missing Authorization
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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