Arc has an authenticated arbitrary local-file read via DuckDB I/O functions that bypasses RBAC table-level checks

### Summary Arc's user-SQL validator (`internal/api/query.go:ValidateSQLRequest`) blocked only `read_parquet(` and `arc_partition_agg(` via regex denylist. The broader DuckDB I/O function family — `read_csv_auto`, `read_csv`, `read_json`, `read_json_auto`, `read_text`, `read_blob`, `glob`, `parquet_metadata`, `parquet_schema`, `read_xlsx`, etc. — was not blocked. RBAC table-reference extraction inspected only `FROM`/`JOIN` clauses, so scalar table functions in the `SELECT` list slipped past both layers. ### Impact Any authenticated user, including a token with `permissions: []`, can read arbitrary local files via: ``` POST /api/v1/query Authorization: Bearer <token> {"sql": "SELECT * FROM read_csv_auto('/etc/passwd', header=false, columns={'l':'VARCHAR'}) LIMIT 5"} ``` Confirmed reachable targets: - `auth.db` — bcrypt hashes for every API token, plus legacy SHA-256 rows. - `arc.toml` — S3 secrets, TLS keys. - `/proc/self/environ` — environment-variable secrets. - Cross-tenant Parquet files — bypasses RBAC because the tenant scope is enforced at the table layer, not on raw file paths. - SSRF when `httpfs` is loaded (any S3-backed deployment) — `read_csv_auto('http://169.254.169.254/latest/meta-data/...')` reaches instance metadata IPs. ### Patches Fixed in 2026.06.1 (PR #442) via a structural sandbox at the DuckDB layer: 1. `SET GLOBAL allowed_directories = [...]` enumerates Arc's legitimate filesystem prefixes (storage roots + tier prefixes + import upload dir + compaction temp). 2. `SET GLOBAL enable_external_access = false` (one-way at runtime). 3. Verified by reading back the flag. After lockdown, DuckDB refuses to open any file outside the allowlist and refuses further `INSTALL`/`LOAD`. Already-loaded extensions remain callable. ### Workarounds - Restrict API access to known-trusted networks via firewall rules. - Temporary mitigation: add `read_csv*`/`read_json*`/`glob` etc. to `dangerousSQLPattern` in `internal/api/query.go` pending 2026.06.1. ### Credits Reported by Alex Manson ([@NeuroWinter](https://github.com/NeuroWinter), https://neurowinter.com/) on 2026-05-19.

Source published

8 Jun 2026 23:51:19 UTC

Source modified

25 Jun 2026 23:11:18 UTC

Observed here

24 Oct 2026 13:19:41 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V4 · CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

Publisher rating · HIGH