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CVE-2026-3115— Guest users can view group member IDs without respecting view restrictions

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公司的一个开源协作平台。 Mattermost存在安全漏洞，该漏洞源于检索组成员ID时未应用视图限制，可能导致经过身份验证的访客用户枚举其可见范围外的用户ID。以下版本受到影响：11.2.2及之前的11.2.x版本、10.11.10及之前的10.11.x版本、11.4.0及之前的11.4.x版本和11.3.1及之前的11.3.x版本。

CVSS 4.3 · Medium EPSS 0.23% · P14

Possible ATT&CK Techniques 1 AI

T1087 · Account Discovery
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I. Basic Information for CVE-2026-3115

Vulnerability Information
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Vulnerability Title
Guest users can view group member IDs without respecting view restrictions
Source: CVE Program / CVE List V5
Vulnerability Description
Mattermost versions 11.2.x <= 11.2.2, 10.11.x <= 10.11.10, 11.4.x <= 11.4.0, 11.3.x <= 11.3.1 fail to apply view restrictions when retrieving group member IDs, which allows authenticated guest users to enumerate user IDs outside their allowed visibility scope via the group retrieval endpoint.. Mattermost Advisory ID: MMSA-2026-00594
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
授权机制不正确
Source: CVE Program / CVE List V5
Vulnerability Title
Mattermost 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Mattermost是美国Mattermost公司的一个开源协作平台。 Mattermost存在安全漏洞，该漏洞源于检索组成员ID时未应用视图限制，可能导致经过身份验证的访客用户枚举其可见范围外的用户ID。以下版本受到影响：11.2.2及之前的11.2.x版本、10.11.10及之前的10.11.x版本、11.4.0及之前的11.4.x版本和11.3.1及之前的11.3.x版本。
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 11.2.0 ~ 11.2.2 -

II. Public POCs for CVE-2026-3115

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III. Intelligence Information for CVE-2026-3115

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Same Patch Batch · Mattermost · 2026-03-26 · 8 CVEs total

CVE-2026-3108 8.0 HIGH Terminal Escape Injection in mmctl Report Posts Command
CVE-2026-3112 6.8 MEDIUM Arbitrary File Read via Advanced Logging Support Packet
CVE-2026-3114 6.5 MEDIUM Zip Bomb Denial of Service via Unrestricted Archive Decompression
CVE-2026-4274 5.4 MEDIUM Insufficient authorization in shared channel membership sync grants team-level access inst
CVE-2026-3113 5.0 MEDIUM mmctl export download command doesn’t restrict permissions to created file to file owner
CVE-2026-3116 4.9 MEDIUM Improper Input Validation in Zoom Plugin Webhook Handler
CVE-2026-3109 2.2 LOW Missing timestamp validation in Zoom webhook handler

IV. Related Vulnerabilities

Same product: Mattermost
Same vendor: Mattermost
Same weakness: CWE-863

V. Comments for CVE-2026-3115

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