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).

CVSS 4.0

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

CVSS 3.1

9.1CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H

EPSS

0.6% chance of exploitation in the next 30 days; higher than 48% of CVEs (scores of 2026-10-26)

CWE

CWE-862

Published

2026-05-11

Modified

2026-10-26

Record from

the NVD, synced 2026-10-26

Affected

• bitwarden:server

References

• https://github.com/bitwarden/server/commit/0918bfdda6f5eec391c69bd9074f6aef4eac0b1d
• https://github.com/bitwarden/server/pull/7372
• https://github.com/bitwarden/server/releases/tag/v2026.4.0
• https://sanjokkarki.com.np/blog/bitwarden-provider-takeover
• https://www.vulncheck.com/advisories/bitwarden-server-missing-authorization-via-provider-clients

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