Is CVE-2026-96259 being exploited?

No public exploit is currently tracked.

How severe is CVE-2026-96259?

CVE-2026-96259 has a CVSS v3 severity of MEDIUM (5.5).

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CVE-2026-96259

Description

Mattermost versions 11.9.x <= 11.9.1, 11.8.x <= 11.8.5, 11.7.x <= 11.7.10, 11.10.x <= 11.10.1 fail to apply the internal-connection filter to OAuth endpoint requests, which allows a System Administrator to make the server issue requests to internal network addresses and read the responses via the configured OAuth token and userinfo endpoints.. Mattermost Advisory ID: MMSA-2026-00776