CVE-2026-12985
Mattermost DCR redirect URI allowlist bypass via improper URL component validation
CVSS Score
6.8
EPSS Score
0.0%
EPSS Percentile
0th
Mattermost 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
| CWE | CWE-601 |
| Vendor | mattermost |
| Product | mattermost |
| Published | Sep 14, 2026 |
| Last Updated | Sep 15, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None
Affected Versions
Mattermost / Mattermost
11.9.0 ≤ 11.9.0 11.8.0 ≤ 11.8.4 11.7.0 ≤ 11.7.7
Credits
aryangurjarf401a3