diff --git a/app/api/auth/register/route.ts b/app/api/auth/register/route.ts
index b45ab46..3303986 100644
--- a/app/api/auth/register/route.ts
+++ b/app/api/auth/register/route.ts
@@ -21,8 +21,8 @@ export async function POST(request: NextRequest) {
         const { name, email, password, inviteCode, invitationToken } = body;
 
         // Validate required fields
-        if (!name || typeof name !== 'string' || name.trim().length < 2) {
-            return apiErrors.badRequest('Name must be at least 2 characters');
+        if (!name || typeof name !== 'string' || name.trim().length < 2 || name.trim().length > 100) {
+            return apiErrors.badRequest('Name must be between 2 and 100 characters');
         }
 
         if (!email || typeof email !== 'string') {
@@ -72,8 +72,8 @@ export async function POST(request: NextRequest) {
             }
         }
 
-        if (!password || typeof password !== 'string' || password.length < 8) {
-            return apiErrors.badRequest('Password must be at least 8 characters');
+        if (!password || typeof password !== 'string' || password.length < 8 || password.length > 128) {
+            return apiErrors.badRequest('Password must be between 8 and 128 characters');
         }
 
         // Check if email already exists
diff --git a/app/api/versions/[versionId]/comments/route.ts b/app/api/versions/[versionId]/comments/route.ts
index 135a733..7fa5ad8 100644
--- a/app/api/versions/[versionId]/comments/route.ts
+++ b/app/api/versions/[versionId]/comments/route.ts
@@ -252,6 +252,17 @@ export async function POST(request: NextRequest, { params }: RouteParams) {
             return apiErrors.badRequest('Either content, a voice recording, an image attachment, or an annotation is required');
         }
 
+        // Length limits to prevent DB bloat and DoS on export/notification paths
+        if (content !== undefined && content !== null && String(content).length > 10_000) {
+            return apiErrors.badRequest('Comment content must be 10,000 characters or fewer');
+        }
+        if (guestName !== undefined && guestName !== null && String(guestName).length > 100) {
+            return apiErrors.badRequest('Guest name must be 100 characters or fewer');
+        }
+        if (annotationData !== undefined && annotationData !== null && JSON.stringify(annotationData).length > 50_000) {
+            return apiErrors.badRequest('Annotation data is too large');
+        }
+
         // If replying, verify parent exists in same version
         if (parentId) {
             const parent = await db.comment.findFirst({
diff --git a/components/guest-gate.tsx b/components/guest-gate.tsx
index a13cbb7..09c715b 100644
--- a/components/guest-gate.tsx
+++ b/components/guest-gate.tsx
@@ -26,8 +26,9 @@ export function GuestGate({ children }: { children: ReactNode }) {
   }
 
   const confirm = () => {
-    if (!guestName.trim()) return;
-    localStorage.setItem('openframe_guest_name', guestName.trim());
+    const trimmed = guestName.trim();
+    if (!trimmed || trimmed.length > 100) return;
+    localStorage.setItem('openframe_guest_name', trimmed);
     setConfirmed(true);
   };
 
@@ -47,13 +48,14 @@ export function GuestGate({ children }: { children: ReactNode }) {
           <Input
             placeholder="Your name"
             value={guestName}
+            maxLength={100}
             onChange={(e) => setGuestName(e.target.value)}
             onKeyDown={(e) => {
               if (e.key === 'Enter') confirm();
             }}
             autoFocus
           />
-          <Button className="w-full" disabled={!guestName.trim()} onClick={confirm}>
+          <Button className="w-full" disabled={!guestName.trim() || guestName.trim().length > 100} onClick={confirm}>
             Continue
           </Button>
         </div>
diff --git a/components/share-link-unlock.tsx b/components/share-link-unlock.tsx
index 0f418af..efbb058 100644
--- a/components/share-link-unlock.tsx
+++ b/components/share-link-unlock.tsx
@@ -61,6 +61,7 @@ export function ShareLinkUnlock({ videoId }: ShareLinkUnlockProps) {
             type="password"
             placeholder="Password"
             value={password}
+            maxLength={128}
             onChange={(event) => setPassword(event.target.value)}
             onKeyDown={(event) => {
               if (event.key === 'Enter') {