ByteOS Network

CVE Vulnerability Details :

CVE-2026-5163

PUBLISHED

More Info Official Page

Assigner-Mattermost

Assigner Org ID-9302f53e-dde5-4bf3-b2f2-a83f91ac0eee

Published At-18 May, 2026 | 08:11

Updated At-18 May, 2026 | 14:40

▼CVE Numbering Authority (CNA)

Missing authorization check in AI message rewrite endpoint allows access to private thread content

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

Affected Products

Vendor

Mattermost, Inc.

Product

Mattermost

Default Status

unaffected

Versions

Affected

From 11.5.0 through 11.5.1 (semver)

Unaffected

11.6.0
11.5.2

Problem Types

Type	CWE ID	Description
CWE	CWE-862	CWE-862: Missing Authorization

Type: CWE

CWE ID: CWE-862

Description: CWE-862: Missing Authorization

Metrics

Version	Base score	Base severity	Vector
3.1	6.5	MEDIUM	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

Version: 3.1

Base score: 6.5

Base severity: MEDIUM

Vector:

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

Solutions

Update Mattermost to versions 11.6.0, 11.5.2 or higher.

Credits

finder

daw10

References

Hyperlink	Resource
https://mattermost.com/security-updates	vendor-advisory

Hyperlink: https://mattermost.com/security-updates

Resource:

vendor-advisory

▼Authorized Data Publishers (ADP)

CISA ADP Vulnrichment

Affected Products

Affected

Unaffected

Problem Types

Metrics

Metrics Other Info

Impacts

Solutions

Configurations

Workarounds

Exploits

Credits

Timeline

Replaced By

Rejected Reason

References

Affected Products

Metrics

Metrics Other Info

Impacts

Solutions

Configurations

Workarounds

Exploits

Credits

Timeline

Replaced By

Rejected Reason

References