Mattermost logs plaintext authentication tokens in debug-level server logs on failed auth attempts

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

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 sanitize authentication tokens before writing them to server log entries, which allows an attacker with access to server logs to obtain valid session tokens or OAuth access tokens and impersonate authenticated users via the debug-level Mattermost server log.. Mattermost Advisory ID: MMSA-2026-00763

Source published

16 Oct 2026 07:07:17 UTC

Source modified

16 Oct 2026 12:02:51 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

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CVSS 3.1 · 4.5 CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:U/C:H/I:N/A:N