CVE-2026-43639

Bitwarden Server broken access control

8.0 HIGHPublic exploitEPSS 0.84%

Published11 May 2026

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).

CVSS 3.1 breakdown

Attack vectorNetwork

Attack complexityHigh

Privileges requiredHigh

User interactionNone

ScopeChanged

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

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

Affected products

Bitwarden Server< 2026.4.0

Remediation

Fixed in

Bitwarden Server≥ 2026.4.0

Patch & vendor advisories

References

https://github.com/bitwarden/server/commit/0918bfdda6f5eec391c69bd9074f6aef4eac0b1dPatch
https://github.com/bitwarden/server/pull/7372Issue TrackingPatch
https://github.com/bitwarden/server/releases/tag/v2026.4.0Release Notes
https://sanjokkarki.com.np/blog/bitwarden-provider-takeoverExploitThird Party Advisory
https://www.vulncheck.com/advisories/bitwarden-server-missing-authorization-via-provider-clientsThird Party Advisory

Related CVEs

Recent high-severity vulnerabilities sharing a weakness type.

Frequently asked

Is CVE-2026-43639 being actively exploited?

CVE-2026-43639 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 0.84%.

How severe is CVE-2026-43639?

CVE-2026-43639 has a CVSS 3.1 base score of 8.0, rated high. EPSS estimates a 0.84% probability of exploitation.

Which products are affected by CVE-2026-43639?

Affected products include Bitwarden Server.

How do I fix CVE-2026-43639?

Upgrade affected software to a fixed version, for example Bitwarden Server 2026.4.0 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-43639 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.