dani-garcia vaultwarden up to 1.35.4 Organization groups_uuid/a collections_groups.collections_uuid improper authorization

Summaryinfo

A vulnerability classified as critical has been found in dani-garcia vaultwarden up to 1.35.4. This issue affects some unknown processing of the component Organization Handler. The manipulation of the argument groups_uuid/a collections_groups.collections_uuid leads to improper authorization. This vulnerability is referenced as CVE-2026-43912. Remote exploitation of the attack is possible. No exploit is available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability was found in dani-garcia vaultwarden up to 1.35.4 and classified as critical. This issue affects some unknown processing of the component Organization Handler. The manipulation of the argument groups_uuid/a collections_groups.collections_uuid with an unknown input leads to a improper authorization vulnerability. Using CWE to declare the problem leads to CWE-285. The product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

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.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-43912 since 05/04/2026. The exploitation is known to be easy. The attack may be initiated remotely. The exploitation requires an enhanced level of successful authentication. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1548.002 according to MITRE ATT&CK.

Upgrading to version 1.35.5 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at CERT Bund (WID-SEC-2026-1285). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Affected

• Open Source Vaultwarden

Productinfo

Vendor

• dani-garcia

Name

• vaultwarden

Version

• 1.35.0
• 1.35.1
• 1.35.2
• 1.35.3
• 1.35.4

Website

• Product: https://github.com/dani-garcia/vaultwarden/

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