CVE-2026-18799 (GCVE-0-2026-18799)
Vulnerability from cvelistv5 – Published: 2026-10-16 07:16 – Updated: 2026-10-16 11:28
VLAI
EPSS
VEX
Title
Mattermost Server fails to restrict Slack import account binding, allowing team admins to forge posts as existing users
Summary
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
Severity
4.3 (Medium)
SSVC
Exploitation: none
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-10-16 11:28 UTC
CWE
- CWE-862 - Missing Authorization
Assigner
References
1 reference
| URL | Tags |
|---|---|
| https://mattermost.com/security-updates | vendor-advisory |
Impacted products
1 product
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| Mattermost | Mattermost |
Affected:
11.10.0 , ≤ 11.10.0
(semver)
Affected: 11.7.0 , ≤ 11.7.9 (semver) Affected: 11.9.0 , ≤ 11.9.1 (semver) Affected: 11.8.0 , ≤ 11.8.5 (semver) Unaffected: 11.11.0 Unaffected: 11.10.1 Unaffected: 11.7.10 Unaffected: 11.9.2 Unaffected: 11.8.6 |
guessed |
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Browse all ATT&CK techniques and the vulnerabilities related to each.
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