Is CVE-2026-16251 being exploited?

No public exploit is currently tracked.

How severe is CVE-2026-16251?

CVE-2026-16251 has a CVSS v3 severity of MEDIUM (6.5).

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CVE-2026-16251

Description

Mattermost versions 11.10.x <= 11.10.0, 11.7.x <= 11.7.9, 11.9.x <= 11.9.1, 11.8.x <= 11.8.5 fail to limit the size of remote image responses buffered in memory during local image proxy direct fetches, which allows a remote attacker to cause memory exhaustion on the server via a crafted oversized image response.. Mattermost Advisory ID: MMSA-2026-00726