CVE intelligence and bounded remediation

CVE-2024-41926 — Mattermost Mattermost Server security vulnerability

Medium CVSS 4.3

Mattermost versions 9.9.x <= 9.9.0 and 9.5.x <= 9.5.6 fail to validate the source of sync messages and only allow the correct remote IDs, which allows a malicious remote to set arbitrary RemoteId values for synced users and therefore claim that a user was synced from another remote.

Severity
Medium
CVSS
4.3 (3.1)
Published
2024-08-01
CISA KEV
Not currently listed
Ecosystem
software/application
Weaknesses
CWE-284, CWE-346

Affected products

  • mattermost / mattermost_server
  • mattermost / mattermost_server / 9.9.0

Matched remediation archetype

Authorization bypass, IDOR, and cross-tenant access

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Check exposure

  • Map object and action authorization checks across API, UI, batch, import/export, and background-job paths.
  • Identify tenant, ownership, role, and policy boundaries for affected resources and administrative operations.
  • Use synthetic fixtures to compare intended access matrices without accessing another user's real data.

Remediate safely

  • Enforce server-side authorization at each resource access and state transition using the authenticated principal and trusted tenant context.
  • Scope data queries by tenant and ownership; treat client-supplied identifiers, roles, and policy claims as untrusted.
  • Add deny-by-default policy tests for horizontal and vertical access across every affected transport.

Authoritative sources

Complete CVE record and remediation plan

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