What’s Vulnerable › Vulnerabilities

CVE-2026-43639: Bitwarden Server < 2026.4.0 Missing Authorization via Provider Clients

• Severity: critical (CVSS 9.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.6% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-05-11 · updated 2026-10-26
• Weakness: CWE-862

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).

Affected products

• bitwarden server: before 2026.4.0 — fixed in 2026.4.0

How to fix

Upgrade to a fixed version: bitwarden server 2026.4.0. Check the vendor advisory for mitigations.

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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