How severe is CVE-2026-43639?

CVE-2026-43639 has a CVSS 3.x base score of 8.0, rated high severity. It is exploitable over network with high attack complexity, requires high privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2026-43639 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (44th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-43639?

CVE-2026-43639 affects Bitwarden Server. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-43639?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-43639 have an EU (EUVD) identifier?

Yes. CVE-2026-43639 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-29170.

When was CVE-2026-43639 published?

CVE-2026-43639 was published on 2026-05-11 and last updated on 2026-06-17.

CVE-2026-43639

CVE-2026-43639 is a high-severity vulnerability in Bitwarden Server with a CVSS 3.x base score of 8.0. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-862.

Key facts

Severity: High (CVSS 3.x base score 8.0)
CVSS v4: 8.9
EPSS exploit prediction: 1% (44th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-29170
Weakness: CWE-862
Affected product: Bitwarden Server
Published: 2026-05-11
Last modified: 2026-06-17

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).

Frequently asked questions

What is 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).
How severe is CVE-2026-43639?: CVE-2026-43639 has a CVSS 3.x base score of 8.0, rated high severity. It is exploitable over network with high attack complexity, requires high privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2026-43639 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (44th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-43639?: CVE-2026-43639 affects Bitwarden Server. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-43639?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-43639 have an EU (EUVD) identifier?: Yes. CVE-2026-43639 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-29170.
When was CVE-2026-43639 published?: CVE-2026-43639 was published on 2026-05-11 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:bitwarden:server:*:*:*:*:*:*:*:*

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CVE-2026-43640 — High (CVSS 8.1): Bitwarden Server prior to v2026.4.1 does not require master-password re-authentication when retrieving or rotating an…
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CVE-2026-57521 — Medium (CVSS 4.3): Bitwarden Server before 2026.5.0 contains a broken access control vulnerability that allows any authenticated user to…

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