Bug 2560533 (CVE-2026-96581)

Summary: CVE-2026-96581 ash: ash: Cross-tenant authorization bypass via unscoped upsert operations
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
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Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in ash. In multitenant configurations, record creation actions configured to update existing entries (upsert) do not properly verify that conflicting records belong to the requesting tenant. An authenticated user can exploit this vulnerability by submitting a record identifier from another tenant during an upsert operation. This allows the attacker to bypass authorization controls, inspect sensitive information, overwrite data, and reassign ownership of records belonging to other tenants.
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Description OSIDB Bzimport 2026-10-26 07:53:14 UTC 
Authorization Bypass Through User-Controlled Key vulnerability in ash-project ash allows a user of one tenant to read, overwrite and take over another tenant's records via an upserting create action.

Under attribute multitenancy, Ash.Actions.Create (lib/ash/actions/create/create.ex) and Ash.Actions.Create.Bulk (lib/ash/actions/create/bulk.ex) upserted on the primary key, or on an all_tenants? identity, without scoping the conflicting record to the request's tenant. A caller of a create action with upsert? true that accepts the primary key, supplying a record id from another tenant, updated that record's upsert fields and received all of its attributes in the result. With the default upsert fields the tenant attribute was written too, moving the record into the caller's tenant. Read and update policies do not run for upserts, and tenant-scoped create policies pass because the tenant is the caller's own.

This issue affects ash: from 1.22.0 before 3.37.2.