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CVE-2026-5163

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CVE-2026-5163

Published: May 18, 2026

Modified: May 18, 2026

PUBLISHED

CVSS v3.1

6.5

MEDIUM

Description

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

VendorProductVersions

Mattermost

Mattermost

affected
11.5.0 - <= 11.5.1
unaffected
11.6.0
unaffected
11.5.2

Weaknesses (CWE)

CWE-862

CVSS v3.1 Details

CVSS v3.1 Vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

None

Availability

None

References

MMSA-2026-00645
vendor-advisory

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