SurrealDB: `RELATE` overwrites existing edge records without `UPDATE` permission

RELATE creates an edge record between two existing records, and SurrealDB enforces the CREATE permission on the edge table for this operation. When the statement included a SET id = edge:existing clause, however, the new edge's id ended up pointing at an record that was already in storage. Rather than failing because the target already existed — which is what a create operation should do — the storage layer silently overwrote the existing edge. A caller with CREATE permission could therefore replace any existing edge on the table, even without UPDATE permission for that record.

Impact

An authenticated user with CREATE permission on an edge table could overwrite any existing record on that table — including edges they had no UPDATE permission for — by issuing a RELATE whose SET id = … resolved to the target record's id. The attack is integrity-only.

Patches

A patch has been introduced that adds an explicit Statement::Relate arm using put_record instead of set_record when the create path is selected. Conflicting writes now return a RecordExists error.

• Versions 3.1.0 and later are not affected by this issue.

This is a behaviour change for applications that relied on RELATE … SET id = … to silently replace existing edges; after the patch those calls return RecordExists instead. Applications that need "create or replace" semantics should use UPSERT (which is correctly permission-gated for the update half).

Workarounds

The defect only fires when the RELATE statement includes a SET id = … clause that resolves to an existing edge id. Applications that let SurrealDB auto-generate the edge id (the default — RELATE a:1 -> edge -> b:1 SET <data> with no id override) are not affected, because auto-generated ids do not collide with existing records.

Where applications must use SET id = … (for example, to produce deterministic edge ids for idempotency), they should first verify that no record with the target id exists before issuing the statement, or restrict CREATE permission on the edge table to principals trusted with UPDATE on the same table.