CVE-2026-43639

High

Description

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).

SeverityHigh

CVSS8.0

Exploit probability—

ProductBitwarden Server

PublishedMay 11, 2026

First seenMay 11, 2026

Weakness typeCWE-862Missing authorization

How to fix

Update

bitwarden server2026.4.0 or later

Patches

github.com/bitwarden/server/commit/0918bfdda6f5eec391c69bd9074f6aef4eac0b1d

Vendor advisories

github.com/bitwarden/server/releases/tag/v2026.4.0

Affected products

Product	Affected versions	Fixed in
bitwarden server	v < 2026.4.0	2026.4.0

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