CVE-2026-43639: Bitwarden Server

Critical severity, CVSS 9.1. EPSS: 0.8% chance of exploitation in the next 30 days.

Bitwarden Server prior to v2026.4.0 contains a missing authorization vulnerability that allows a provider service user to add an arbitrary organization to their provider via `POST /providers/{providerId}/clients/existing`, resulting in takeover of the target organization; self-hosted installations are unaffected as this endpoint is restricted to Cloud via SelfHosted(NotSelfHostedOnly = true).

Affected products

• Bitwarden Server: before 2026.4.0 (fixed in 2026.4.0)

Published 2026-05-11. Last modified 2026-07-14.