Unauthorized Access Issue in Mattermost for Users with Manager Role
CVE-2026-9820

3.8LOW

Key Information:

Vendor

Mattermost
Status
Mattermost
Vendor
CVE Published:
13 July 2026

What is CVE-2026-9820?

Mattermost versions 11.7.x (up to 11.7.2) and 10.11.x (up to 10.11.19) exhibit a flaw that fails to properly sanitize team objects returned by the API endpoint. This oversight allows users assigned as User Managers to generate invite links for private teams. Consequently, they can gain unapproved access to these private teams, compromising the confidentiality of sensitive team information. Organizations using affected versions should apply the necessary updates to mitigate any potential unauthorized access.

Affected Version(s)

Mattermost 11.7.0 <= 11.7.2

Mattermost 10.11.0 <= 10.11.19

Mattermost 11.8.0

References

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

CVSS V3.1

Score:
3.8
Severity:
LOW
Confidentiality:
Low
Integrity:
Low
Availability:
Low
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
High
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

0x7oda7123
.