fix(core): Prevent prototype pollution in task runner (#12588)

docker/images/n8n/n8n-task-runners.json

@@ -6,6 +6,7 @@
 			"command": "/usr/local/bin/node",
 			"args": [
 				"--disallow-code-generation-from-strings",
+				"--disable-proto=delete",
 				"/usr/local/lib/node_modules/n8n/node_modules/@n8n/task-runner/dist/start.js"
 			],
 			"allowed-env": [

packages/@n8n/task-runner/src/js-task-runner/__tests__/js-task-runner.test.ts

@@ -1342,4 +1342,75 @@ describe('JsTaskRunner', () => {
 			task.cleanup();
 		});
 	});
+
+	describe('prototype pollution prevention', () => {
+		const checkPrototypeIntact = () => {
+			const obj: Record<string, unknown> = {};
+			expect(obj.maliciousKey).toBeUndefined();
+		};
+
+		test('Object.setPrototypeOf should no-op for local object', async () => {
+			checkPrototypeIntact();
+
+			const outcome = await executeForAllItems({
+				code: `
+					const obj = {};
+					Object.setPrototypeOf(obj, { maliciousKey: 'value' });
+					return [{ json: { prototypeChanged: obj.maliciousKey !== undefined } }];
+				`,
+				inputItems: [{ a: 1 }],
+			});
+
+			expect(outcome.result).toEqual([wrapIntoJson({ prototypeChanged: false })]);
+			checkPrototypeIntact();
+		});
+
+		test('Reflect.setPrototypeOf should no-op for local object', async () => {
+			checkPrototypeIntact();
+
+			const outcome = await executeForAllItems({
+				code: `
+					const obj = {};
+					Reflect.setPrototypeOf(obj, { maliciousKey: 'value' });
+					return [{ json: { prototypeChanged: obj.maliciousKey !== undefined } }];
+				`,
+				inputItems: [{ a: 1 }],
+			});
+
+			expect(outcome.result).toEqual([wrapIntoJson({ prototypeChanged: false })]);
+			checkPrototypeIntact();
+		});
+
+		test('Object.setPrototypeOf should no-op for incoming object', async () => {
+			checkPrototypeIntact();
+
+			const outcome = await executeForAllItems({
+				code: `
+					const obj = $input.first();
+					Object.setPrototypeOf(obj, { maliciousKey: 'value' });
+					return [{ json: { prototypeChanged: obj.maliciousKey !== undefined } }];
+				`,
+				inputItems: [{ a: 1 }],
+			});
+
+			expect(outcome.result).toEqual([wrapIntoJson({ prototypeChanged: false })]);
+			checkPrototypeIntact();
+		});
+
+		test('Reflect.setPrototypeOf should no-op for incoming object', async () => {
+			checkPrototypeIntact();
+
+			const outcome = await executeForAllItems({
+				code: `
+					const obj = $input.first();
+					Reflect.setPrototypeOf(obj, { maliciousKey: 'value' });
+					return [{ json: { prototypeChanged: obj.maliciousKey !== undefined } }];
+				`,
+				inputItems: [{ a: 1 }],
+			});
+
+			expect(outcome.result).toEqual([wrapIntoJson({ prototypeChanged: false })]);
+			checkPrototypeIntact();
+		});
+	});
 });

packages/@n8n/task-runner/src/js-task-runner/js-task-runner.ts

@@ -103,6 +103,20 @@ export class JsTaskRunner extends TaskRunner {
 			allowedBuiltInModules: parseModuleAllowList(jsRunnerConfig.allowedBuiltInModules ?? ''),
 			allowedExternalModules: parseModuleAllowList(jsRunnerConfig.allowedExternalModules ?? ''),
 		});
+
+		this.preventPrototypePollution();
+	}
+
+	private preventPrototypePollution() {
+		if (process.env.NODE_ENV === 'test') return; // needed for Jest
+
+		Object.getOwnPropertyNames(globalThis)
+			// @ts-expect-error globalThis does not have string in index signature
+			// eslint-disable-next-line @typescript-eslint/no-unsafe-return, @typescript-eslint/no-unsafe-member-access
+			.map((name) => globalThis[name])
+			.filter((value) => typeof value === 'function')
+			// eslint-disable-next-line @typescript-eslint/no-unsafe-return, @typescript-eslint/no-unsafe-member-access
+			.forEach((fn) => Object.freeze(fn.prototype));
 	}
 
 	async executeTask(
@@ -203,8 +217,11 @@ export class JsTaskRunner extends TaskRunner {
 
 				signal.addEventListener('abort', abortHandler, { once: true });
 
+				const preventPrototypeManipulation =
+					'Object.getPrototypeOf = () => ({}); Reflect.getPrototypeOf = () => ({}); Object.setPrototypeOf = () => false; Reflect.setPrototypeOf = () => false;';
+
 				const taskResult = runInContext(
-					`globalThis.global = globalThis; module.exports = async function VmCodeWrapper() {${settings.code}\n}()`,
+					`globalThis.global = globalThis; ${preventPrototypeManipulation}; module.exports = async function VmCodeWrapper() {${settings.code}\n}()`,
 					context,
 					{ timeout: this.taskTimeout * 1000 },
 				) as Promise<TaskResultData['result']>;

packages/cli/src/task-runners/__tests__/task-runner-process.test.ts

@@ -118,13 +118,14 @@ describe('TaskRunnerProcess', () => {
 			expect(options.env).not.toHaveProperty('NODE_OPTIONS');
 		});
 
-		it('should use --disallow-code-generation-from-strings flag', async () => {
+		it('should use --disallow-code-generation-from-strings and --disable-proto=delete flags', async () => {
 			jest.spyOn(authService, 'createGrantToken').mockResolvedValue('grantToken');
 
 			await taskRunnerProcess.start();
 
 			expect(spawnMock.mock.calls[0].at(1)).toEqual([
 				'--disallow-code-generation-from-strings',
+				'--disable-proto=delete',
 				expect.stringContaining('/packages/@n8n/task-runner/dist/start.js'),
 			]);
 		});

packages/cli/src/task-runners/task-runner-process.ts

@@ -106,9 +106,13 @@ export class TaskRunnerProcess extends TypedEmitter<TaskRunnerProcessEventMap> {
 	startNode(grantToken: string, taskBrokerUri: string) {
 		const startScript = require.resolve('@n8n/task-runner/start');
 
-		return spawn('node', ['--disallow-code-generation-from-strings', startScript], {
+		return spawn(
+			'node',
+			['--disallow-code-generation-from-strings', '--disable-proto=delete', startScript],
+			{
 				env: this.getProcessEnvVars(grantToken, taskBrokerUri),
-		});
+			},
+		);
 	}
 
 	@OnShutdown()