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

High severity GitHub Reviewed Published May 31, 2026 in Basekick-Labs/arc • Updated Jun 8, 2026

Package

gomod github.com/basekick-labs/arc (Go)

Affected versions

< 0.0.0-20260520141557-91bdc29d1a02

Patched versions

0.0.0-20260520141557-91bdc29d1a02

Description

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://neurowinter.com/) on 2026-05-19.

References

@xe-nvdk xe-nvdk published to Basekick-Labs/arc May 31, 2026
Published to the GitHub Advisory Database Jun 8, 2026
Reviewed Jun 8, 2026
Last updated Jun 8, 2026

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Network
Attack Complexity Low
Attack Requirements None
Privileges Required Low
User interaction None
Vulnerable System Impact Metrics
Confidentiality High
Integrity None
Availability None
Subsequent System Impact Metrics
Confidentiality None
Integrity None
Availability None

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
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

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(8th percentile)

Weaknesses

Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory. Learn more on MITRE.

Exposure of Sensitive Information to an Unauthorized Actor

The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information. Learn more on MITRE.

Server-Side Request Forgery (SSRF)

The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination. Learn more on MITRE.

CVE ID

CVE-2026-47735

GHSA ID

GHSA-p2j4-c4g6-rpf5

Source code

Credits

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