Junglewise Threat Intelligence

CVE-2026-43639: Bitwarden Server missing authorization in provider clients endpoint

CVE-2026-43639 · Severity: high · CVSS 8 · Published 2026-05-11

Executive brief

Bitwarden Server, the backend for the Bitwarden password management service, contained a security flaw in its provider management interface. This vulnerability allowed a malicious provider service user to unauthorizedly link and take control of other organizations within the Bitwarden Cloud environment. An exploit could lead to a full takeover of a target organization's data and settings, though self-hosted installations are not affected.

Technical details

A missing authorization check (CWE-862) existed in the Bitwarden Server's provider controller. Specifically, the `POST /providers/{providerId}/clients/existing` endpoint failed to properly validate the permissions of a provider service user before allowing them to associate an existing organization with their provider ID. By exploiting this, an attacker with provider-level access could gain administrative control over arbitrary organizations. The vulnerability is restricted to the Cloud environment as the affected endpoint is configured with `NotSelfHostedOnly = true`. The issue was resolved in version 2026.4.0 by implementing stricter role handling and authorization checks in the provider controllers.

Affected products

  • Bitwarden Bitwarden Server prior to v2026.4.0

Timeline

  • 2026-04-01: patched: Fix merged via pull request 7372
  • 2026-04-15: advisory: Release v2026.4.0 published
  • 2026-05-11: disclosed: CVE-2026-43639 published to NVD

References