Auth bypass in Bitwarden Server
CVE-2026-43639
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).
Vulnerability class: Broken Access Control
Published · last modified .
CVSS v3 metric
CVSS v3 base score 8.0 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.006 (47.2th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 47th percentile — 47.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.006 · newest: 0.006 · change: 0.000
Affected products
- Bitwarden Server — versions 0
Weakness classification (CWE)
References
- sanjokkarki.com.np/blog/bitwarden-provider-takeover (Exploit, technical-description, Third Party Advisory, exploit)
- github.com/bitwarden/server/releases/tag/v2026.4.0 (release-notes, Release Notes)
- github.com/bitwarden/server/pull/7372 (issue-tracking, Patch, Issue Tracking)
- github.com/bitwarden/server/commit/0918bfdda6f5eec391c69bd9074f6aef4eac0b1d (Patch, patch)
- www.vulncheck.com/advisories/bitwarden-server-missing-authorization-via-provide… (Third Party Advisory, third-party-advisory)
Frequently asked questions
- What is CVE-2026-43639?
- CVE-2026-43639 is a high-severity vulnerability in Bitwarden Server, classified under Missing Authorization. CVSS score: 8.0/10. Published 2026-05-11.
- How severe is CVE-2026-43639?
- High severity. CVSS v3 base score is 8.0 out of 10.