Is github.com/mattermost/mattermost/server/v8 affected by CVE-2026-3115?

Go github.com/mattermost/mattermost/server/v8 is affected in >=11.4.0 =11.3.0-rc1 =11.2.0-rc1 =10.11.0-rc1 =8.0.0-20260105080200-d27a2195068d <8.0.0-20260217110922-b7d4a1f1f59b.

Is CVE-2026-3115 being exploited?

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

medium

CVE-2026-3115

Q: Is CVE-2026-3115 being exploited?

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

Go · github.com/mattermost/mattermost/server/v8

Summary

Mattermost allows authenticated guest users to enumerate user IDs outside their allowed visibility scope

Severity: medium
EPSS: 0.2% (p14)
Also known as: GHSA-mpc7-mm28-f6wq
Published: 2026-03-26

References

Related advisories

CVE-2026-6346 — high · Go/github.com/mattermost/mattermost/server/v8
CVE-2026-3108 — high · Go/github.com/mattermost/mattermost/server/v8
CVE-2026-6339 — medium · Go/github.com/mattermost/mattermost/server/v8
CVE-2026-6343 — medium · Go/github.com/mattermost/mattermost/server/v8
CVE-2026-5163 — medium · Go/github.com/mattermost/mattermost/server/v8
CVE-2026-28732 — medium · Go/github.com/mattermost/mattermost/server/v8
CVE-2026-6345 — medium · Go/github.com/mattermost/mattermost/server/v8
CVE-2026-6340 — medium · Go/github.com/mattermost/mattermost/server/v8

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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.