Loading a through relationship with a limit of 1 in Ash ignores the through path and returns unrelated destination records

Overview

Incorrect Authorization vulnerability in ash-project ash allows a client to read destination records unrelated to the source record through a through relationship.

When a has_many relationship declared with through: was loaded for a single record with a limit of 1, or an unsorted has_one through relationship was loaded with a limit of 1, lateral_join?/4 in lib/ash/actions/read/relationships.ex chose the path that reads the destination without any filter linking it to the source. The load returned the first destination record by sort, or any other record with an offset. The read still runs the destination's policies but carries the relationship as accessing_from, so a client paging such a field (for example teachers(limit: 1, offset: n) through AshGraphql) can enumerate destination records that policies allow only when reached through that relationship.

This issue affects ash: from 3.24.0 before 3.37.1.

Affected

• ash >= 3.24.0 < 3.37.1
• ash-project/ash >= 24f41e23dcbd9d07cde270a8141490e8f79251f5 < e37463307304b26bc8fd606322e5c4d8f7f060e5

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.