23 Oct 2026 15:48:27 UTC
Mattermost DCR redirect URI allowlist bypass via improper URL component validation
cve-program · CVE-2026-12985 · Published
CVE-2026-12985
Mattermost DCR redirect URI allowlist bypass via improper URL component validation
CVSS 3.1 6.8 MEDIUMCheck source for fixed versionsKEV status unknown
cve-program · CVE-2026-12985
PublishedMattermost versions 11.9.x <= 11.9.0, 11.8.x <= 11.8.4, 11.7.x <= 11.7.7 Mattermost failed to validate Dynamic Client Registration redirect URIs by URL component (matching glob patterns against the raw URI string instead) which allows a remote unauthenticated attacker to register an OAuth client with an attacker-controlled callback host that bypasses the configured redirect URI allowlist via a crafted redirect URI that places an allowlisted host/path suffix inside the query string.. Mattermost Advisory ID: MMSA-2026-00700
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