CVE-2026-93596: medium-severity vulnerability in ArcadeData arcadedb

ArcadeDB before 26.9.1 (com.arcadedb:arcadedb-engine <= 26.8.1) fails to bind the authenticated principal onto the DatabaseAsyncTransaction async worker threads used by the parallel edge-connect phase of POST /api/v1/batch/{database}. Because those workers have no current user, LocalDatabase.checkPermissionsOnFile returns early and allows the write, bypassing per-type CREATE_RECORD/UPDATE_RECORD ACL enforcement. In deployments that rely on per-type or per-group ACLs, an authenticated low-privilege user holding CREATE_RECORD on an edge type E but with CREATE_RECORD/UPDATE_RECORD revoked on a vertex type V can submit a graph edge-load batch request (with parallelFlush at its default value of true) and durably append edges to protected vertices of type V by writing records into V's <V>_out_edges/<V>_in_edges buckets, resulting in unauthorized modification of graph adjacency. Setting parallelFlush=false causes the request to be correctly rejected. This is an incomplete fix of GHSA-c23x-pqcj-7hfm, which bound the principal only on the HTTP handler thread.