@grackle-ai/mcp Workspace Authorization Bypass in knowledge_search MCP Tool

The @grackle-ai/mcp package, specifically versions 0.70.1 and earlier, contains a critical authorization bypass vulnerability within the knowledge_search and knowledge_get_node MCP tools. This vulnerability allows scoped agents operating within one workspace to circumvent intended isolation boundaries and access knowledge graph nodes residing in other workspaces. This is due to the knowledge_search and knowledge_get_node handlers failing to properly receive or enforce workspace scoping via the authContext. This vulnerability poses a significant risk of cross-workspace data leakage in deployments where multiple workspaces contain sensitive knowledge graph data and scoped agents are utilized. The issue was reported on March 25, 2026, and is tracked as GHSA-647h-p824-99w7. Defenders should prioritize patching or implementing workarounds to mitigate this risk.

Attack Chain

1. A scoped agent is deployed within Workspace A, possessing limited permissions within that workspace.
2. The attacker identifies the presence of the knowledge_search and knowledge_get_node tools within the SCOPED_TOOLS set, indicating their accessibility to scoped agents.
3. The attacker crafts a request to the knowledge_search or knowledge_get_node handler, supplying an arbitrary workspaceId parameter corresponding to Workspace B.
4. Due to the missing authContext and lack of workspace scoping enforcement in the handler, the request bypasses intended access controls.
5. The handler retrieves knowledge graph nodes from Workspace B based on the attacker-supplied workspaceId.
6. The data from Workspace B is returned to the scoped agent in Workspace A.
7. The attacker gains unauthorized access to sensitive knowledge graph data residing in Workspace B.
8. The attacker can exfiltrate or misuse the compromised data, leading to data leakage or other malicious activities.

Impact

This vulnerability results in cross-workspace data leakage, potentially exposing sensitive information stored in knowledge graphs across different workspaces. The number of affected deployments depends on the adoption rate of @grackle-ai/mcp with scoped agents and multi-workspace configurations. Successful exploitation can lead to unauthorized access to confidential data, impacting data privacy, compliance, and potentially causing reputational damage. The vulnerability affects any deployment where multiple workspaces contain sensitive knowledge graph data and scoped agents are used, putting organizations at significant risk.

Recommendation

• Upgrade @grackle-ai/mcp to a patched version beyond 0.70.1 to address the authorization bypass vulnerability.
• As a temporary workaround, remove knowledge_search and knowledge_get_node from the SCOPED_TOOLS set in tool-scoping.ts to restrict access to these tools for scoped agents.
• Monitor the usage of knowledge_search and knowledge_get_node handlers for requests originating from scoped agents, and alert on any attempts to access knowledge graph nodes from different workspaces.
• If scoped agents are not currently used in multi-workspace deployments, consider disabling them temporarily until the patch is applied.