CVE-2026-75845: ArcadeDB Authorization Bypass Vulnerability

CVE-2026-75845 Overview

ArcadeDB versions 26.4.2 through 26.7.3 contain an authorization bypass in the Model Context Protocol (MCP) server-level tool set_server_setting. The SetServerSettingTool.execute() method gates access only on the global allowAdmin flag and never validates the caller's role. In MCP deployments configured with allowAdmin=true and a non-root allowedUsers set, any authenticated read-only user can invoke set_server_setting to modify server GlobalConfiguration. This enables configuration tampering and denial-of-service conditions. The issue is fixed in version 26.8.1. The weakness is tracked as improper privilege management [CWE-269].

Critical Impact
Authenticated low-privilege users can modify server-wide configuration, causing configuration tampering or denial of service against ArcadeDB instances exposing the MCP interface.

Affected Products

ArcadeDB 26.4.2 through 26.7.3
ArcadeDB MCP server deployments with allowAdmin=true
ArcadeDB deployments using a non-root allowedUsers set

Discovery Timeline

2026-08-18 - CVE-2026-75845 published to NVD
2026-08-18 - Last updated in NVD database

Technical Details for CVE-2026-75845

Vulnerability Analysis

ArcadeDB exposes administrative functions through an MCP interface, including the set_server_setting tool. This tool is intended for administrators to modify runtime GlobalConfiguration values on the server. The implementation in SetServerSettingTool.execute() performs a single check against the global allowAdmin boolean flag. It never inspects the identity or role of the authenticated caller invoking the tool. As a result, the tool treats any authenticated session as authorized whenever allowAdmin is enabled at the server level.

Successful invocation permits mutation of server-wide configuration keys. Attackers can adjust operational parameters, disable protective settings, or force the database into a degraded state. The impact spans confidentiality, integrity, and availability at a limited scope, consistent with configuration tampering on a shared database instance.

Root Cause

The root cause is missing role-based authorization on a privileged MCP tool handler. The code path relies solely on a global feature flag intended to advertise administrative capability rather than to enforce per-caller access control. Read-only accounts included in allowedUsers inherit administrative reach through this omission.

Attack Vector

Exploitation requires network access to the MCP endpoint and valid credentials for any account in the allowedUsers set. The attacker authenticates with read-only credentials and issues an MCP tool call to set_server_setting with an attacker-chosen configuration key and value. No user interaction is required. See the GitHub Security Advisory and the VulnCheck Advisory on ArcadeDB for additional technical detail.

Detection Methods for CVE-2026-75845

Indicators of Compromise

MCP tool invocations of set_server_setting originating from non-administrator accounts.
Unexpected changes to GlobalConfiguration values in ArcadeDB server logs.
Server restarts, degraded performance, or configuration drift shortly after read-only user activity.

Detection Strategies

Audit ArcadeDB server logs for calls to SetServerSettingTool correlated with the invoking user's role.
Alert on configuration mutations from any account not explicitly designated as root or administrator.
Compare running GlobalConfiguration state against a known-good baseline on a scheduled basis.

Monitoring Recommendations

Forward ArcadeDB and MCP endpoint logs to a centralized analytics platform for correlation with identity events.
Track authentication events for accounts in allowedUsers and flag privileged tool invocations by low-privilege users.
Monitor for anomalous MCP tool-call patterns, especially those targeting server-level tools.

How to Mitigate CVE-2026-75845

Immediate Actions Required

Upgrade ArcadeDB to version 26.8.1 or later, which enforces role checks in SetServerSettingTool.execute().
Inventory MCP deployments and identify any instance running 26.4.2 through 26.7.3 with allowAdmin=true.
Rotate credentials for accounts in allowedUsers if server logs show unexpected set_server_setting activity.

Patch Information

The issue is resolved in ArcadeDB 26.8.1. Refer to the GitHub Security Advisory GHSA-pff6-hp53-pj54 for the fix commit and release notes.

Workarounds

Set allowAdmin=false on MCP deployments where administrative tools are not required.
Restrict allowedUsers to accounts that are trusted with administrative access until the upgrade is applied.
Place the MCP endpoint behind network controls that limit access to administrator workstations.

bash

# Configuration example
# Disable the allowAdmin flag on the MCP server until the upgrade to 26.8.1 is applied
# Edit the ArcadeDB server configuration and set:
#   allowAdmin=false
# Then restart the ArcadeDB service to apply the change.