Goal Reached Thanks to every supporter — we hit 100%!

Goal: 1000 CNY · Raised: 1359 CNY

100%
Buy Us a Coffee

CVE-2026-4274— Insufficient authorization in shared channel membership sync grants team-level access instead of channel-level access

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 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版本存在安全漏洞，该漏洞源于处理来自远程集群的成员同步时未能限制团队级访问，可能导致恶意远程集群通过发送特制的成员同步消息授予用户访问整个私有团队的权限。

CVSS 5.4 · Medium EPSS 0.23% · P13

Possible ATT&CK Techniques 1 AI

T1199 · Trusted Relationship
Get alerts for future matching vulnerabilities Log in to subscribe

I. Basic Information for CVE-2026-4274

Vulnerability Information
Have questions about the vulnerability? See if Shenlong's analysis helps!
View Shenlong Deep Dive ↗

Although we use advanced large model technology, its output may still contain inaccurate or outdated information.Shenlong tries to ensure data accuracy, but please verify and judge based on the actual situation.

Vulnerability Title
Insufficient authorization in shared channel membership sync grants team-level access instead of channel-level access
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 restrict team-level access when processing membership sync from a remote cluster, which allows a malicious remote cluster to grant a user access to an entire private team instead of only the shared channel via sending crafted membership sync messages that trigger team membership assignment. Mattermost Advisory ID: MMSA-2026-00574
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/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 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版本存在安全漏洞，该漏洞源于处理来自远程集群的成员同步时未能限制团队级访问，可能导致恶意远程集群通过发送特制的成员同步消息授予用户访问整个私有团队的权限。
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-2026-4274

# POC Description Source Link Shenlong Link
AI-Generated POC Premium

No public POC found.

Login to generate AI POC

III. Intelligence Information for CVE-2026-4274

请登录查看更多情报信息。

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-2026-3113 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-2026-3115 4.3 MEDIUM Guest users can view group member IDs without respecting view restrictions
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-2026-4274

No comments yet

Leave a comment