VulnerabilityPublished 2 Jul 2026

@grackle-ai/mcp · Grackle: Fail-open authorization

Affects @grackle-ai/mcpSource GCVE Database

CVSS 8.7 High.

Data as of 3 Jul 2026, 22:49 UTC

CVSS 4.0 base score

8.7High

How severe the flaw is on the 0–10 CVSS scale.

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: Low
User Interaction: None
Vulnerable system confidentiality: High
Vulnerable system integrity: High
Vulnerable system availability: High
Subsequent system confidentiality: None
Subsequent system integrity: None
Subsequent system availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: Low: The attacker requires privileges that provide basic capabilities that are typically limited to settings and resources owned by a single low-privileged user. Alternatively, an attacker with Low privileges has the ability to access only non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable system confidentiality: High: There is a total loss of confidentiality, resulting in all information within the Vulnerable System being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact. For example, an attacker steals the administrator's password, or private encryption keys of a web server.
Vulnerable system integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the vulnerable system. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the vulnerable system.
Vulnerable system availability: High: There is a total loss of availability, resulting in the attacker being able to fully deny access to resources in the Vulnerable System; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the Vulnerable System (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: None: There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.

Definitions: FIRST CVSS v4.0 specification.

What to do

Affected software

Product	Affected	Fixed in
npm@grackle-ai/mcp	Affected <=0.132.1	Fixed in–
npm@grackle-ai/plugin-core	Affected <=0.132.1	Fixed in–
npm@grackle-ai/auth	Affected <=0.132.1	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

The advisory recommends a systemic fix to enforce scope centrally in the MCP tool request dispatcher, ensuring any tool targeting a task or session fails closed unless the caller is an ancestor or self. Immediate mitigation includes adding ancestry checks (assertCallerIsAncestor) to all mutating tools lacking them (task_update, task_delete, task_resume, session_kill, session_resume). Scoped tokens without workspace association should be treated as having no workspace access, enforcing membership checks on all relevant tools. The scoped-token revocation mechanism should be integrated into task lifecycle flows with persistent storage or removed if unused. Until fixes are applied, restrict use of scoped agents and monitor for unauthorized cross-task or cross-session operations.

Description

## 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

Impact

Scoped agents can bypass authorization controls to perform unauthorized mutations across tasks and sessions, including deleting or updating tasks belonging to other agents or workspaces, and terminating or resuming sessions they do not own. This leads to privilege boundary bypass, potential data loss, and denial of service against sibling or parent agents. Workspaceless scoped tokens allow read-only disclosure of all tasks across all workspaces. The ineffective token revocation means compromised scoped tokens remain valid for their full lifetime, increasing risk of persistent unauthorized access.

CWE-613DEPRECATED: Insufficient Session Expiration (opens in a new tab)
Base weaknessOWASP Top 10 A07:2025: Authentication Failures (opens in a new tab)
This entry has been deprecated because it was insufficiently clear. Consider CWE-1462 and its descendants.
MITRE does not allow mapping vulnerabilities to this entry; it groups weaknesses rather than naming one.
OWASP Cheat Sheets
OWASP Authentication (opens in a new tab)
OWASP ASVS 4.0.3
V2.8.1 (opens in a new tab)
V2.8.6 (opens in a new tab)
V3.6.1 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-639Authorization Bypass Through User-Controlled Key (opens in a new tab)
Base weaknessLikelihood of exploit: HighCWE Top 25 (2025): #24OWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The system's authorization functionality does not prevent one user from gaining access to another user's data or record by modifying the key value identifying the data.
Architecture and Design
For each and every data access, ensure that the user has sufficient privilege to access the record that is being requested.
Architecture and Design · Implementation
Make sure that the key that is used in the lookup of a specific user's record is not controllable externally by the user or that any tampering can be detected.
Architecture and Design
Use encryption in order to make it more difficult to guess other legitimate values of the key or associate a digital signature with the key so that the server can verify that there has been no tampering.
OWASP Cheat Sheets
Access Control (opens in a new tab)
Authorization Testing Automation (opens in a new tab)
Cross-Site Request Forgery Prevention (opens in a new tab)
Insecure Direct Object Reference Prevention (opens in a new tab)
Authorization (opens in a new tab)
OWASP ASVS 4.0.3
V4.1.2 (opens in a new tab)
V4.2.1 (opens in a new tab)
V8.3.8 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-862Missing Authorization (opens in a new tab)
Class weaknessLikelihood of exploit: HighCWE Top 25 (2025): #4OWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The product does not perform an authorization check when an actor attempts to access a resource or perform an action.
Architecture and Design
Divide the product into anonymous, normal, privileged, and administrative areas. Reduce the attack surface by carefully mapping roles with data and functionality. Use role-based access control (RBAC) to enforce the roles at the appropriate boundaries.
Architecture and Design
Ensure that access control checks are performed related to the business logic. These checks may be different than the access control checks that are applied to more generic resources such as files, connections, processes, memory, and database records.
Architecture and Design · Libraries or Frameworks
Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
OWASP Cheat Sheets
Authorization (opens in a new tab)
OWASP ASVS 4.0.3
V8.3.8 (opens in a new tab)
V13.4.2 (opens in a new tab)
V7.2.2 (opens in a new tab)
Attack patterns
Exploitation of Thunderbolt Protection Flaws (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

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What to do

Affected software

Description

AI analysisMachine-generated, updated 2 Jul 2026, 23:12 UTC

WeaknessesCWE-613, CWE-639, CWE-862

Technical details

References

Community reviews

Related threats