CVE-2026-5163

Mattermost versions 11.5.x <= 11.5.1 fail to verify channel membership when processing AI-assisted message rewrites which allows an authenticated attacker to read the content of threads in private channels and direct messages they do not have access to via a crafted request to the post rewrite endpoint.. Mattermost Advisory ID: MMSA-2026-00645

CVSS v3 6.5 MEDIUM

6.5^/10

CVSS v3 : MEDIUM

Vector :

Exploitability : 2.8 / Impact : 3.6

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required LOW

User Interaction NONE

Confidentiality Impact HIGH

Integrity Impact NONE

Availability Impact NONE

Scope UNCHANGED

References

Link	Resource
https://mattermost.com/security-updates	Vendor Advisory

Configurations

Configuration 1 (hide)

cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*

History

No history.

Information

Published : 2026-05-18 09:16

Updated : 2026-06-17 10:58

NVD link : CVE-2026-5163

Mitre link : CVE-2026-5163

CVE.ORG link : CVE-2026-5163

JSON object : View

Products Affected

mattermost

mattermost_server

CWE

CWE-862

Missing Authorization

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