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CVE-2026-6046— Plugin bot username conflict allows user account to be used as bot identity in Mattermost Server

Quick assessment

Affected
Mattermost Mattermost
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Mattermost是美国Mattermost公司开源的一个开源协作平台。 Mattermost 11.6.1及之前的11.6.x版本、11.5.4及之前的11.5.x版本、10.11.15及之前的10.11.x版本和10.11.16及之前的10.11.x版本存在信息泄露漏洞，该漏洞源于未验证机器人注册时返回的用户名是否属于机器人账户，可能导致低权限攻击者通过预注册具有可预测插件机器人用户名的用户账户来拦截插件通过直接消息频道发送的私人消息。

CVSS 5.3 · Medium EPSS 0.30% · P22

Affected Version Matrix 9

VendorProduct Version RangeStatus
Mattermost Mattermost 11.6.0≤ 11.6.1 affected
11.5.0≤ 11.5.4 affected
10.11.0≤ 10.11.15 affected
10.11.0≤ 10.11.16 affected
11.7.0 unaffected
11.6.2 unaffected
11.5.5 unaffected
10.11.16 unaffected
… +1 more rows
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I. Basic Information for CVE-2026-6046

Vulnerability Information
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Vulnerability Title
Plugin bot username conflict allows user account to be used as bot identity in Mattermost Server
Source: CVE Program / CVE List V5
Vulnerability Description
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 validate that a username returned during bot registration belongs to a bot account, which allows an unprivileged attacker to intercept private messages sent by plugins via direct message channels by pre-registering a user account with a predictable plugin bot username.. Mattermost Advisory ID: MMSA-2026-00649
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
信息暴露
Source: CVE Program / CVE List V5
Vulnerability Title
Mattermost 信息泄露漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Mattermost是美国Mattermost公司开源的一个开源协作平台。 Mattermost 11.6.1及之前的11.6.x版本、11.5.4及之前的11.5.x版本、10.11.15及之前的10.11.x版本和10.11.16及之前的10.11.x版本存在信息泄露漏洞，该漏洞源于未验证机器人注册时返回的用户名是否属于机器人账户，可能导致低权限攻击者通过预注册具有可预测插件机器人用户名的用户账户来拦截插件通过直接消息频道发送的私人消息。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Mattermost Mattermost 11.6.0 ~ 11.6.1 -

II. Public POCs for CVE-2026-6046

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III. Intelligence Information for CVE-2026-6046

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Same Patch Batch · Mattermost · 2026-06-12 · 7 CVEs total

CVE-2026-7387 8.8 HIGH Mattermost group syncable endpoints allow privilege escalation via scheme_admin
CVE-2026-6961 7.6 HIGH CVE-2026-6961: Path traversal via unsanitized FileInfo.Name in Mattermost federation sync
CVE-2026-6739 6.7 MEDIUM Mattermost: Delegated admins could patch protected default system roles
CVE-2026-7184 6.5 MEDIUM Mattermost Remote Cluster PATCH API Leaks Authentication Tokens
CVE-2026-6689 4.3 MEDIUM *Missing* {{invite_user}} *permission check on team creation allows unprivileged users to
CVE-2026-3433 4.3 MEDIUM Mattermost fails to scope role_updated websocket events to authorized team and channel mem

IV. Related Vulnerabilities

Same product: Mattermost
Same vendor: Mattermost
Same weakness: CWE-200

V. Comments for CVE-2026-6046

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