PT-2026-57594 · Npm · @Grackle-Ai/Auth+2

Published

2026-07-02

·

Updated

2026-07-02

CVSS v4.0

8.7

High

VectorAV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Summary

Authorization for scoped (agent) MCP callers is enforced inline, per tool, and is applied inconsistently — several mutating tools silently omit the ancestry/workspace check that their siblings perform. Because the MCP server authenticates all outbound gRPC with the full server API key and the backend gRPC handlers perform no caller-based authorization, the MCP tool layer is the sole authorization boundary. A malicious or prompt-injected scoped agent can therefore perform cross-task and cross-session operations it should not be allowed to (an IDOR / privilege-boundary bypass).
This advisory bundles the audit's Systemic Pattern A findings: F2, F6, F7, F12 (and the duplicate F19).

Affected versions

@grackle-ai/mcp (with @grackle-ai/plugin-core / @grackle-ai/auth) at 0.132.1 and earlier.

Root cause

  • mcp-server.ts:111-127 (createGrpcClients) sets Authorization: Bearer ${apiKey} (the full server key) on every outbound gRPC call.
  • Backend handlers (updateTask, deleteTask, resumeTask, killAgent, getTask in plugin-core) take only the request message — no AuthContext — and act on whatever ID is passed.
  • Therefore scope must be enforced in each MCP tool handler. Some call assertCallerIsAncestor (task complete, task start, session attach, session send input); their destructive siblings do not. New tools that forget the check fail open.

F2 — task update / task delete / task resume bypass ancestry (High)

Location: packages/mcp/src/tools/task.ts:226 (task update), :393 (task delete), :465 (task resume).
These accept an arbitrary taskId with only a ROOT TASK ID special-case and no assertCallerIsAncestor. The central dispatcher hardcodes its workspace gate to name === "task show", and these tools' Zod schemas have no workspaceId field (so the blanket injection is stripped). They are not in DEFAULT SCOPED MCP TOOLS but are in the shipped ORCHESTRATOR MCP TOOLS / ADMIN MCP TOOLS presets.
Exploit: a scoped agent under the orchestrator persona learns a sibling/parent/cross-workspace task ID (via task list/task search), then task delete {taskId: <victim>} (permanently destroys another agent's or the human parent's work) or task update to flip a sibling to complete/failed or rewrite its dependency DAG and budgets.

F6 — session kill / session resume bypass ancestry (Medium)

Location: packages/mcp/src/tools/session.ts:95 (session resume), :178 (session kill).
Call client.killAgent / client.resumeAgent directly with no auth context, unlike session attach/session send input. session kill is in the orchestrator preset. Exploit: cross-session SIGKILL DoS against a sibling agent or the root orchestrator; foreign session resume.

F7 — Workspaceless scoped token fails open to all workspaces (Medium)

Location: packages/mcp/src/mcp-server.ts:565-600.
The per-task cross-workspace check (task show block) is gated on authContext.workspaceId being truthy. A task created without a workspace (a supported config) mints a scoped token with pid: "" → workspaceId: undefined, so the check is skipped and the injected workspaceId becomes "", which the backend treats as "all workspaces." Exploit: a malicious agent in a workspaceless session calls task list (no args) → reads every task in every workspace, then task show {taskId} cross-workspace (title/description/branch/review-notes). schedule show (in the default scoped allowlist) resolves by ID with no workspace check. Read-only cross-workspace disclosure.

F12 — Scoped-token revocation is dead code (Low)

Location: packages/auth/src/scoped-token.ts:23,142-149.
The consuming check is wired (auth-middleware.ts:90-92), but revokeTask() is never called outside tests — no task-abort/stop flow invokes it — and the backing revokedTasks Map is in-memory only (lost on restart). A compromised agent that exfiltrated its scoped token keeps authenticating for the full 24h TTL regardless of task lifecycle.

Remediation

  • Systemic fix: enforce scope centrally in the CallToolRequest dispatcher (mcp-server.ts) via a per-tool targetTaskIdArg / targetSessionIdArg descriptor so any tool that targets a task/session fails closed unless the caller is an ancestor (or self).
  • Immediately, add assertCallerIsAncestor (or self-or-ancestor) to task update, task delete, task resume, session kill, session resume, mirroring task complete/task start.
  • F7: do not fail open on empty workspaceId — treat a scoped non-root caller with no workspace as having access to no workspace; apply the task show membership check whenever the caller is scoped and not ROOT TASK ID; add a per-id membership check to schedule show.
  • F12: wire revokeTask() into task-abort/stop flows with SQLite-backed persistence (like channel-grant revocation), or remove the dead API and document the 24h window.
  • Add regression tests mirroring the existing task complete ancestor tests for each mutator.

CWEs

CWE-862 (Missing Authorization), CWE-639 (Authorization Bypass Through User-Controlled Key / IDOR), CWE-613 (Insufficient Session Expiration).

Fix

IDOR

Missing Authorization

Insufficient Session Expiration

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Weakness Enumeration

CWE-639CWE-862CWE-613

Related Identifiers

GHSA-F9FF-5X35-7GFW

Affected Products

@Grackle-Ai/Auth
@Grackle-Ai/Mcp
@Grackle-Ai/Plugin-Core