NocoDB: Shared-base link access can invite arbitrary users as persistent base members

Summary

Shared-base sessions were granted the same base-member capabilities as authenticated viewers. Using only the shared-base UUID (xc-shared-base-id), an attacker could enumerate base members and invite an arbitrary email into the base as a real member. The invited user could then redeem the invite via the normal signup flow and retain authenticated access even after the owner revoked the shared link.

Details

Shared-base sessions were mapped to ProjectRoles.VIEWER in packages/nocodb/src/strategies/base-view.strategy/base-view.strategy.ts, and packages/nocodb/src/utils/acl.ts granted baseUserList and userInvite to that role. The shared frontend (packages/nc-gui/composables/useApi/interceptors.ts) deliberately removed auth headers in favour of the shared-base header, but the ACL middleware did not distinguish shared sessions from genuine viewers.

The end-to-end chain:

• GET /api/v2/meta/bases/:baseId/users returned the member list to shared-base callers (@Acl('baseUserList')).
• POST /api/v2/meta/bases/:baseId/users accepted an invite from shared-base callers (@Acl('userInvite')); base-users.service.ts inserted a real nc_users_v2 row with invite_token and a nc_base_users_v2 row for the target base, with invited_by = null.
• The invited account redeemed the invite through the normal signup path (users.service.ts), gaining a persistent JWT scoped to the base.
• Revoking the shared link did not affect the redeemed account.

Impact

• Confidentiality: shared-base link exposes member email addresses.
• Integrity: shared-base link can mutate base ACL state by creating new members.
• Persistence: link-based access converts into durable authenticated access that survives revocation of the share.

Credit

This issue was reported by @0xmrma.