CVE-2026-18799

MediumCVSS 4.3/10Last modified Oct 29, 2026

Description

Mattermost versions 11.10.x <= 11.10.0, 11.7.x <= 11.7.9, 11.9.x <= 11.9.1, 11.8.x <= 11.8.5 fail to restrict Slack import account binding to system administrator-initiated imports which allows an authenticated attacker with team admin privileges to force-add existing Mattermost users to their team and forge posts attributed to those users' identities via a crafted Slack export containing target users' email addresses.. Mattermost Advisory ID: MMSA-2026-00757

Metrics

CVSS 3.1 4.3/10CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N

Weakness enumeration

CWE-862

Affected software

Vendor	Product	Versions
Mattermost	Mattermost	>= 11.10.0, <= 11.10.0; >= 11.7.0, <= 11.7.9; >= 11.9.0, <= 11.9.1; >= 11.8.0, <= 11.8.5

References

https://mattermost.com/security-updatesVendor Advisory

Timeline

Published: Oct 16, 2026
Last modified: Oct 29, 2026
NVD status: Analyzed

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