diff --git a/keyserver/src/endpoints.js b/keyserver/src/endpoints.js
--- a/keyserver/src/endpoints.js
+++ b/keyserver/src/endpoints.js
@@ -57,6 +57,7 @@
   oldPasswordUpdateResponder,
   updateUserSettingsResponder,
   policyAcknowledgmentResponder,
+  updateUserAvatarResponder,
 } from './responders/user-responders.js';
 import { codeVerificationResponder } from './responders/verification-responders.js';
 import { uploadDeletionResponder } from './uploads/uploads.js';
@@ -242,6 +243,10 @@
     responder: siweAuthResponder,
     requiredPolicies: [],
   },
+  update_user_avatar: {
+    responder: updateUserAvatarResponder,
+    requiredPolicies: baseLegalPolicies,
+  },
 };
 
 export { jsonEndpoints };
diff --git a/keyserver/src/responders/user-responders.js b/keyserver/src/responders/user-responders.js
--- a/keyserver/src/responders/user-responders.js
+++ b/keyserver/src/responders/user-responders.js
@@ -26,6 +26,7 @@
   notificationTypeValues,
   logInActionSources,
 } from 'lib/types/account-types.js';
+import type { UpdateUserAvatarRequest } from 'lib/types/avatar-types.js';
 import type {
   IdentityKeysBlob,
   SignedIdentityKeysBlob,
@@ -42,6 +43,7 @@
   SubscriptionUpdateResponse,
 } from 'lib/types/subscription-types.js';
 import type { PasswordUpdate } from 'lib/types/user-types.js';
+import { updateUserAvatarRequestValidator } from 'lib/utils/avatar-utils.js';
 import {
   identityKeysBlobValidator,
   signedIdentityKeysBlobValidator,
@@ -670,6 +672,14 @@
   await viewerAcknowledgmentUpdater(viewer, request.policy);
 }
 
+async function updateUserAvatarResponder(
+  viewer: Viewer,
+  input: any,
+): Promise<void> {
+  const request: UpdateUserAvatarRequest = input;
+  await validateInput(viewer, updateUserAvatarRequestValidator, request);
+}
+
 export {
   userSubscriptionUpdateResponder,
   passwordUpdateResponder,
@@ -683,4 +693,5 @@
   oldPasswordUpdateResponder,
   updateUserSettingsResponder,
   policyAcknowledgmentResponder,
+  updateUserAvatarResponder,
 };
diff --git a/lib/types/endpoints.js b/lib/types/endpoints.js
--- a/lib/types/endpoints.js
+++ b/lib/types/endpoints.js
@@ -83,6 +83,7 @@
   VERIFY_CODE: 'verify_code',
   SIWE_NONCE: 'siwe_nonce',
   SIWE_AUTH: 'siwe_auth',
+  UPDATE_USER_AVATAR: 'update_user_avatar',
 });
 type SocketPreferredEndpoint = $Values<typeof socketPreferredEndpoints>;