Is github.com/mattermost/mattermost-server affected by CVE-2026-20796?

Go github.com/mattermost/mattermost-server is affected in >=10.11.0+incompatible <10.11.10+incompatible.

Is CVE-2026-20796 being exploited?

Not on the CISA KEV list. EPSS exploit probability is 0.2%.

medium

CVE-2026-20796

Q: Is CVE-2026-20796 being exploited?

Not on the CISA KEV list. EPSS exploit probability is 0.2%.

Go · github.com/mattermost/mattermost-server

Summary

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

Severity: medium
EPSS: 0.2% (p10)
Also known as: GHSA-2xf7-hmf6-p64j, GO-2026-4495
Published: 2026-02-23

References

Related advisories

CVE-2026-6346 — high · Go/github.com/mattermost/mattermost-server
CVE-2026-6347 — high · Go/github.com/mattermost/mattermost-server
CVE-2026-6339 — medium · Go/github.com/mattermost/mattermost-server
CVE-2026-5163 — medium · Go/github.com/mattermost/mattermost-server
CVE-2026-28732 — medium · Go/github.com/mattermost/mattermost-server
CVE-2026-6345 — medium · Go/github.com/mattermost/mattermost-server
CVE-2026-6340 — medium · Go/github.com/mattermost/mattermost-server
CVE-2026-3637 — medium · Go/github.com/mattermost/mattermost-server

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Sources: CISA KEV (public domain), OSV.dev & GitHub Advisory Database (CC-BY-4.0), FIRST EPSS, NVD/CWE (public domain). Served live from the Stateward advisory database.