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CVE PROGRAM SOURCE RECORD6.8 Medium

CVE-2026-12985

Mattermost DCR redirect URI allowlist bypass via improper URL component validation

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Status
Published
Published
Updated
Assigning organization
Mattermost

Description

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

Affected products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

Mattermost Mattermost

Default version status: unaffected

  • 11.9.0 to ≤ 11.9.0affected
  • 11.8.0 to ≤ 11.8.4affected
  • 11.7.0 to ≤ 11.7.7affected
  • 11.10.0unaffected
  • 11.9.1unaffected
  • 11.8.5unaffected
  • 11.7.8unaffected

References