CVE-2026-6345Network attack vector

User impersonation via disclosed generated passwords

Published May 18, 2026 · Updated May 18, 2026

Insufficient credential protection in affected Mattermost releases allows remote authenticated users to impersonate newly created users. Mattermost has not disclosed where the account-creation workflow exposes generated passwords or how those credentials become accessible. Exploitation requires high privileges and yields access to affected imported accounts, without reported service interruption.

CVSS severity6.5
Medium
EPSS probability0.23%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Insufficient credential protection in affected Mattermost releases allows remote authenticated users to impersonate newly created users. Mattermost has not disclosed where the account-creation workflow exposes generated passwords or how those credentials become accessible. Exploitation requires high privileges and yields access to affected imported accounts, without reported service interruption.

The record

CVE
CVE-2026-6345
Published
May 18, 2026
Updated
May 18, 2026
Vendor
Mattermost
Product
Mattermost
Classifications
CWE-522, T1078
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. May 18, 2026CVE publishedPublication date reported by the CVE source.
  2. May 18, 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 <=10.11.13
  2. Affected versionversion=11.4.0 <=11.4.3
  3. Affected versionversion=11.5.0 <=11.5.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesadmin

What is affected?

Mattermost · Mattermostversion=10.11.0 <=10.11.13; version=11.4.0 <=11.4.3; version=11.5.0 <=11.5.1

Published CVSS scores

6.5Mattermost, Inc.CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/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
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-522Insufficiently Protected Credentials
T1078Valid Accounts

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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