Arc contains a cross‑database authorization bypass that allows an attacker to execute DuckDB table‑valued I/O functions from a tenant’s query context without proper tenant authorization. This flaw can be exploited through crafted SQL statements sent to the /api/v1/query endpoint, enabling the attacker to read other tenants’ time‑series data, enumerate schemas, and retrieve per‑column statistics. The vulnerability is the result of a missing denylist for several I/O aliases such as parquet_scan, glob, parquet_metadata, parquet_schema, read_blob, read_csv_auto, read_json, and read_text, after the remediation of an earlier CVE. The weakness is classified as Information Exposure (CWE‑200) and Authorization Bypass (CWE‑863).

The issue affects Basekick‑Labs Arc versions prior to 26.06.2, including the 26.06.1 release and earlier builds. The 26.06.2 tag includes the necessary I/O function repair and boundary fixes.

The CVSS score of 6.5 indicates moderate severity. EPSS data is unavailable, but the flaw is not listed in CISA KEV, suggesting no widespread exploitation yet. The likely attack vector is sending malicious SQL to the REST API, and the attack requires authentication but can be leveraged by a compromised tenant account or an attacker who gains access to the API endpoint.