CVE-2026-5163 (GCVE-0-2026-5163)

Vulnerability from cvelistv5 – Published: 2026-05-18 08:11 – Updated: 2026-05-18 14:40
VLAI
Title
Missing authorization check in AI message rewrite endpoint allows access to private thread content
Summary
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
Severity
6.5 (Medium)
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-05-18 14:39 UTC
CWE
Assigner
Mattermost CNA under the mitre root
CNA scorecard B 80/100 over 107 records in the last 180 days details
References
URL Tags
https://mattermost.com/security-updates vendor-advisory
Impacted products
Vendor Product Version CPE status
Mattermost Mattermost Affected: 11.5.0 , ≤ 11.5.1 (semver)
Unaffected: 11.6.0
Unaffected: 11.5.2
guessed Create a notification for this product.
Credits
daw10
Show details on NVD website
To clipboard 

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