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CVE-2026-20796 Low

Mattermost doesn't properly validate channel membership at the time of data retrieval in github.com/mattermost/mattermost-server

Mattermost doesn't properly validate channel membership at the time of data retrieval in github.com/mattermost/mattermost-server

Exploit probability 0.2%
Published February 23, 2026
Required by Not available
Last source change February 23, 2026

02 / AFFECTED SOFTWARE

Affected packages

Unknown Unknown

21 explicit affected versions

Go github.com/mattermost/mattermost-server
Go github.com/mattermost/mattermost-server

03 / CONNECTIONS

Connected vulnerabilities

related OPENSUSE-SU-2026:21483-1

04 / EVIDENCE

Source records

Open Source Vulnerabilities CVE-2026-20796

Mattermost versions 10.11.x <= 10.11.9 fail to properly validate channel membership at the time of data retrieval which allows a deactivated user to learn team names they should not have access to via a race condition in the /common_teams API endpoint.. Mattermost Advisory ID: MMSA-2025-00549

View original source
Open Source Vulnerabilities GO-2026-4495

Mattermost doesn't properly validate channel membership at the time of data retrieval in github.com/mattermost/mattermost-server

View original source
Open Source Vulnerabilities GHSA-2xf7-hmf6-p64j

Mattermost versions 10.11.x <= 10.11.9 fail to properly validate channel membership at the time of data retrieval which allows a deactivated user to learn team names they should not have access to via a race condition in the /common_teams API endpoint.. Mattermost Advisory ID: MMSA-2025-00549

View original source

05 / REFERENCES

Further evidence