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Description

Mattermost versions 11.7.x <= 11.7.2, 11.6.x <= 11.6.4, 10.11.x <= 10.11.19 fail to validate that an assigned incoming webhook user has access to the target team or channel, which allows a requester with webhook management permissions to create posts or direct messages attributed to another user via crafted incoming webhook configuration and payloads.. Mattermost Advisory ID: MMSA-2026-00683

PUBLISHED Reserved 2026-05-27 | Published 2026-07-13 | Updated 2026-07-13 | Assigner Mattermost




MEDIUM: 4.9CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:N

Problem types

CWE-639: Authorization Bypass Through User-Controlled Key

Product status

Default status
unaffected

11.7.0 (semver)
affected

11.6.0 (semver)
affected

10.11.0 (semver)
affected

11.8.0
unaffected

11.7.3
unaffected

11.6.5
unaffected

10.11.20
unaffected

Credits

arang finder

References

mattermost.com/security-updates (MMSA-2026-00683) vendor-advisory

cve.org (CVE-2026-9708)

nvd.nist.gov (CVE-2026-9708)

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