diff --git a/packages/syncing-server/bin/server.ts b/packages/syncing-server/bin/server.ts
index 76fddb593..cbd77e6e5 100644
--- a/packages/syncing-server/bin/server.ts
+++ b/packages/syncing-server/bin/server.ts
@@ -4,7 +4,7 @@ import 'newrelic'
 
 import '../src/Controller/HealthCheckController'
 import '../src/Controller/ItemsController'
-import '../src/Controller/ItemSharesController'
+import '../src/Controller/SharingController'
 
 import helmet from 'helmet'
 import * as cors from 'cors'
diff --git a/packages/syncing-server/src/Bootstrap/ServerContainerConfigLoader.ts b/packages/syncing-server/src/Bootstrap/ServerContainerConfigLoader.ts
index 25853ea92..fce0f8ec6 100644
--- a/packages/syncing-server/src/Bootstrap/ServerContainerConfigLoader.ts
+++ b/packages/syncing-server/src/Bootstrap/ServerContainerConfigLoader.ts
@@ -1,5 +1,5 @@
-import { UpdateSharedItemUseCase } from './../Domain/UseCase/ItemShare/UpdateSharedItemUseCase'
-import { GetSharedItemUseCase } from './../Domain/UseCase/ItemShare/GetSharedItemUseCase'
+import { UpdateSharedItemUseCase } from '../Domain/UseCase/Sharing/UpdateSharedItemUseCase'
+import { GetSharedItemUseCase } from '../Domain/UseCase/Sharing/GetSharedItemUseCase'
 import { ItemShareServiceInterface } from '../Domain/ItemShare/Service/ItemShareServiceInterface'
 import { Container, interfaces } from 'inversify'
 
@@ -34,8 +34,8 @@ import { ItemConflictProjection } from '../Projection/ItemConflictProjection'
 import { CommonContainerConfigLoader } from './CommonContainerConfigLoader'
 import { ItemShareService } from '../Domain/ItemShare/Service/ItemShareService'
 import { ItemShareFactory } from '../Domain/ItemShare/Factory/ItemShareFactory'
-import { ShareItemUseCase } from '../Domain/UseCase/ItemShare/ShareItemUseCase'
-import { GetUserItemSharesUseCase } from '../Domain/UseCase/ItemShare/GetUserItemSharesUseCase'
+import { ShareItemUseCase } from '../Domain/UseCase/Sharing/ShareItemUseCase'
+import { GetUserItemSharesUseCase } from '../Domain/UseCase/Sharing/GetUserItemSharesUseCase'
 import { TokenEncoder, TokenEncoderInterface, ValetTokenData } from '@standardnotes/security'
 import { CreateSharedFileValetToken } from '../Domain/UseCase/CreateSharedFileValetToken/CreateSharedFileValetToken'
 import { ItemShareFactoryInterface } from '../Domain/ItemShare/Factory/ItemShareFactoryInterface'
diff --git a/packages/syncing-server/src/Controller/ItemsController.ts b/packages/syncing-server/src/Controller/ItemsController.ts
index 48f9a1a53..28bf59191 100644
--- a/packages/syncing-server/src/Controller/ItemsController.ts
+++ b/packages/syncing-server/src/Controller/ItemsController.ts
@@ -78,9 +78,18 @@ export class ItemsController extends BaseHttpController {
     })
 
     if (!result.success) {
-      return this.notFound()
+      return this.notFoundJson()
     }
 
     return this.json({ item: await this.itemProjector.projectFull(result.item) })
   }
+
+  private notFoundJson(): results.JsonResult {
+    return this.json(
+      {
+        error: { message: 'Item not found' },
+      },
+      404,
+    )
+  }
 }
diff --git a/packages/syncing-server/src/Controller/ItemSharesController.ts b/packages/syncing-server/src/Controller/SharingController.ts
similarity index 67%
rename from packages/syncing-server/src/Controller/ItemSharesController.ts
rename to packages/syncing-server/src/Controller/SharingController.ts
index a541c8c7b..6f3e68181 100644
--- a/packages/syncing-server/src/Controller/ItemSharesController.ts
+++ b/packages/syncing-server/src/Controller/SharingController.ts
@@ -1,22 +1,24 @@
-import { GetUserItemSharesUseCase } from './../Domain/UseCase/ItemShare/GetUserItemSharesUseCase'
-import { UpdateSharedItemUseCase } from './../Domain/UseCase/ItemShare/UpdateSharedItemUseCase'
-import { GetSharedItemUseCase } from './../Domain/UseCase/ItemShare/GetSharedItemUseCase'
+import { GetUserItemSharesUseCase } from '../Domain/UseCase/Sharing/GetUserItemSharesUseCase'
+import { UpdateSharedItemUseCase } from '../Domain/UseCase/Sharing/UpdateSharedItemUseCase'
+import { GetSharedItemUseCase } from '../Domain/UseCase/Sharing/GetSharedItemUseCase'
 import { Request, Response } from 'express'
 import { inject } from 'inversify'
 import { BaseHttpController, controller, httpGet, httpPatch, httpPost, results } from 'inversify-express-utils'
 import TYPES from '../Bootstrap/Types'
-import { ShareItemUseCase } from '../Domain/UseCase/ItemShare/ShareItemUseCase'
+import { ShareItemUseCase } from '../Domain/UseCase/Sharing/ShareItemUseCase'
 import { CreateSharedFileValetToken } from '../Domain/UseCase/CreateSharedFileValetToken/CreateSharedFileValetToken'
 import { ContentType } from '@standardnotes/common'
 import { ProjectorInterface } from '../Projection/ProjectorInterface'
 import { Item } from '../Domain/Item/Item'
 import { ItemProjection } from '../Projection/ItemProjection'
+import { GetItem } from '../Domain/UseCase/GetItem/GetItem'
 
 @controller('/sharing')
-export class ItemSharesController extends BaseHttpController {
+export class SharingController extends BaseHttpController {
   constructor(
     @inject(TYPES.ShareItem) private shareItem: ShareItemUseCase,
     @inject(TYPES.GetSharedItem) private getSharedItem: GetSharedItemUseCase,
+    @inject(TYPES.GetItem) private getItem: GetItem,
     @inject(TYPES.UpdateSharedItem) private updateSharedItem: UpdateSharedItemUseCase,
     @inject(TYPES.GetUserItemShares) private getItemShares: GetUserItemSharesUseCase,
     @inject(TYPES.CreateSharedFileValetToken) private createSharedFileValetToken: CreateSharedFileValetToken,
@@ -26,7 +28,20 @@ export class ItemSharesController extends BaseHttpController {
   }
 
   @httpPost('/', TYPES.AuthMiddleware)
-  public async share(request: Request, response: Response): Promise<results.JsonResult> {
+  public async share(request: Request, response: Response): Promise<results.NotFoundResult | results.JsonResult> {
+    const getItemResponse = await this.getItem.execute({
+      userUuid: response.locals.user.uuid,
+      itemUuid: request.body.itemUuid,
+    })
+
+    if (getItemResponse.success === false) {
+      return this.notFoundJson()
+    }
+
+    if (getItemResponse.item.userUuid !== response.locals.user.uuid) {
+      return this.notFoundJson()
+    }
+
     const result = await this.shareItem.execute({
       itemUuid: request.body.itemUuid,
       userUuid: response.locals.user.uuid,
@@ -41,7 +56,25 @@ export class ItemSharesController extends BaseHttpController {
   }
 
   @httpPatch('/', TYPES.AuthMiddleware)
-  public async updateSharedItemRequest(request: Request): Promise<results.JsonResult> {
+  public async updateSharedItemRequest(
+    request: Request,
+    response: Response,
+  ): Promise<results.NotFoundResult | results.JsonResult> {
+    const getItemResponse = await this.getSharedItem.execute({
+      shareToken: request.body.shareToken,
+    })
+
+    if (getItemResponse.success === false) {
+      return this.json({
+        success: false,
+        message: 'Could not find shared item',
+      })
+    }
+
+    if (getItemResponse.item.userUuid !== response.locals.user.uuid) {
+      return this.notFoundJson()
+    }
+
     const result = await this.updateSharedItem.execute({
       shareToken: request.body.shareToken,
       encryptedContentKey: request.body.encryptedContentKey,
@@ -57,14 +90,14 @@ export class ItemSharesController extends BaseHttpController {
     })
 
     if (result.success === false) {
-      return this.notFound()
+      return this.notFoundJson()
     }
 
     const item = await this.itemProjector.projectFull(result.item)
 
     if (result.item.contentType === ContentType.File) {
       if (!result.itemShare.fileRemoteIdentifier) {
-        return this.notFound()
+        return this.notFoundJson()
       }
 
       const valetTokenResult = await this.createSharedFileValetToken.execute({
@@ -81,15 +114,15 @@ export class ItemSharesController extends BaseHttpController {
       }
 
       return this.json({
-        itemShare: result.itemShare,
         item,
+        itemShare: result.itemShare,
         fileValetToken: valetTokenResult.valetToken,
       })
     }
 
     return this.json({
-      itemShare: result.itemShare,
       item,
+      itemShare: result.itemShare,
     })
   }
 
@@ -103,9 +136,18 @@ export class ItemSharesController extends BaseHttpController {
     })
 
     if (result.success === false) {
-      return this.notFound()
+      return this.notFoundJson()
     }
 
     return this.json(result)
   }
+
+  private notFoundJson(): results.JsonResult {
+    return this.json(
+      {
+        error: { message: 'Not found' },
+      },
+      404,
+    )
+  }
 }
diff --git a/packages/syncing-server/src/Domain/UseCase/CreateSharedFileValetToken/CreateSharedFileValetToken.ts b/packages/syncing-server/src/Domain/UseCase/CreateSharedFileValetToken/CreateSharedFileValetToken.ts
index 70e644970..140855439 100644
--- a/packages/syncing-server/src/Domain/UseCase/CreateSharedFileValetToken/CreateSharedFileValetToken.ts
+++ b/packages/syncing-server/src/Domain/UseCase/CreateSharedFileValetToken/CreateSharedFileValetToken.ts
@@ -6,7 +6,7 @@ import { CreateValetTokenResponseData } from '@standardnotes/responses'
 import TYPES from '../../../Bootstrap/Types'
 import { UseCaseInterface } from '../UseCaseInterface'
 import { CreateSharedFileValetTokenDTO } from './CreateSharedFileValetTokenDTO'
-import { GetSharedItemUseCase } from '../ItemShare/GetSharedItemUseCase'
+import { GetSharedItemUseCase } from '../Sharing/GetSharedItemUseCase'
 
 @injectable()
 export class CreateSharedFileValetToken implements UseCaseInterface {
diff --git a/packages/syncing-server/src/Domain/UseCase/ItemShare/GetSharedItemUseCase.ts b/packages/syncing-server/src/Domain/UseCase/Sharing/GetSharedItemUseCase.ts
similarity index 100%
rename from packages/syncing-server/src/Domain/UseCase/ItemShare/GetSharedItemUseCase.ts
rename to packages/syncing-server/src/Domain/UseCase/Sharing/GetSharedItemUseCase.ts
diff --git a/packages/syncing-server/src/Domain/UseCase/ItemShare/GetUserItemSharesUseCase.ts b/packages/syncing-server/src/Domain/UseCase/Sharing/GetUserItemSharesUseCase.ts
similarity index 100%
rename from packages/syncing-server/src/Domain/UseCase/ItemShare/GetUserItemSharesUseCase.ts
rename to packages/syncing-server/src/Domain/UseCase/Sharing/GetUserItemSharesUseCase.ts
diff --git a/packages/syncing-server/src/Domain/UseCase/ItemShare/ShareItemUseCase.ts b/packages/syncing-server/src/Domain/UseCase/Sharing/ShareItemUseCase.ts
similarity index 100%
rename from packages/syncing-server/src/Domain/UseCase/ItemShare/ShareItemUseCase.ts
rename to packages/syncing-server/src/Domain/UseCase/Sharing/ShareItemUseCase.ts
diff --git a/packages/syncing-server/src/Domain/UseCase/ItemShare/UpdateSharedItemUseCase.ts b/packages/syncing-server/src/Domain/UseCase/Sharing/UpdateSharedItemUseCase.ts
similarity index 100%
rename from packages/syncing-server/src/Domain/UseCase/ItemShare/UpdateSharedItemUseCase.ts
rename to packages/syncing-server/src/Domain/UseCase/Sharing/UpdateSharedItemUseCase.ts