Authentication Bypass Vulnerability in Mattermost by Mattermost Inc.
CVE-2026-0999

5.4MEDIUM

Key Information:

Vendor

Mattermost
Status
Mattermost
Vendor
CVE Published:
16 February 2026

What is CVE-2026-0999?

Mattermost has identified a vulnerability in versions 11.1.x up to 11.1.2, 10.11.x up to 10.11.9, and 11.2.x up to 11.2.1 where userID-based authentication does not adequately enforce Single Sign-On (SSO) login requirements. This weakness allows authenticated users to bypass the intended security mechanism, potentially leading to unauthorized access. It is critical to apply the necessary updates to safeguard against this vulnerability.

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Affected Version(s)

Mattermost 11.1.0 <= 11.1.2

Mattermost 10.11.0 <= 10.11.9

Mattermost 11.2.0 <= 11.2.1

References

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

CVSS V3.1

Score:
5.4
Severity:
MEDIUM
Confidentiality:
Low
Integrity:
Low
Availability:
Low
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
Low
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

daw10
JSON
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