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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).

PUBLISHED Reserved 2026-05-01 | Published 2026-05-11 | Updated 2026-05-11 | Assigner VulnCheck




HIGH: 8.9CVSS:4.0/AV:N/AC:H/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H

HIGH: 8.0CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H

Problem types

Missing Authorization

Product status

Default status
affected

Any version before 2026.4.0
affected

Credits

Sanjok Karki finder

References

sanjokkarki.com.np/blog/bitwarden-provider-takeover technical-description exploit

github.com/bitwarden/server/releases/tag/v2026.4.0 release-notes

github.com/bitwarden/server/pull/7372 issue-tracking

github.com/...ommit/0918bfdda6f5eec391c69bd9074f6aef4eac0b1d patch

www.vulncheck.com/...sing-authorization-via-provider-clients third-party-advisory

cve.org (CVE-2026-43639)

nvd.nist.gov (CVE-2026-43639)

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