Bug 2476356 (CVE-2026-43912)

Summary: CVE-2026-43912 vaultwarden: Vaultwarden: Unauthorized vault data access via improper organization consistency enforcement
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Priority: high    
Version: unspecifiedKeywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in Vaultwarden, a Bitwarden-compatible server. A remote attacker with administrative privileges in one organization and low-privileged membership in another could exploit improper enforcement of organization consistency in group management endpoints. This allows the attacker to bind their low-privileged membership to a group in the administrative organization. Consequently, the attacker gains unauthorized read and write access to vault data, including ciphers and items, in the low-privileged organization.
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Bug Depends On: 2476447, 2476448    
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Description OSIDB Bzimport 2026-05-11 23:03:08 UTC 
Vaultwarden is a Bitwarden-compatible server written in Rust. Prior to 1.35.5, Vaultwarden does not enforce that a groups_users.users_organizations_uuid entry belongs to the same organization as groups.groups_uuid, or a collections_groups.collections_uuid entry belongs to the same organization as collections_groups.groups_uuid. Multiple organization group-management endpoints accept arbitrary MembershipId and CollectionId values and persist them directly without verifying org consistency. This lets an attacker who is Admin in Organization A, and only a low-privileged member in Organization B bind their Org B membership UUID into an Org A group, then use that foreign group relationship to gain unauthorized access to Org B vault data. With an accessAll=true Org A group, the attacker can make /api/sync and /api/ciphers enumerate Org B ciphers. Once those unauthorized sync results reveal Org B collection IDs, the attacker can also bind those foreign collection IDs to the Org A group and turn the same flaw into write access over Org B items. This vulnerability is fixed in 1.35.5.