diff --git a/src/live2dcubismframework.ts b/src/live2dcubismframework.ts
index ada25a8..adde886 100644
--- a/src/live2dcubismframework.ts
+++ b/src/live2dcubismframework.ts
@@ -16,7 +16,9 @@ import { Value } from './utils/cubismjson';
 
 export function strtod(s: string, endPtr: string[]): number {
   let index = 0;
-  for (let i = 1; ; i++) {
+  // Bound the scan: once i exceeds s.length, substring clamps and a complete
+  // number never becomes NaN, so an unbounded loop never terminates.
+  for (let i = 1; i <= s.length; i++) {
     const testC: string = s.slice(i - 1, i);
 
     // 指数・マイナスの可能性があるのでスキップする
diff --git a/src/utils/cubismjson.ts b/src/utils/cubismjson.ts
index e87c5e9..e4251ff 100644
--- a/src/utils/cubismjson.ts
+++ b/src/utils/cubismjson.ts
@@ -390,8 +390,11 @@ export class CubismJson {
         case '8':
         case '9': {
           const afterString: string[] = new Array(1); // 参照渡しにするため
-          f = strtod(buffer.slice(i), afterString);
-          outEndPos[0] = buffer.indexOf(afterString[0]);
+          const numericSlice = buffer.slice(i);
+          f = strtod(numericSlice, afterString);
+          // afterString[0] が空だと indexOf('') は 0 を返し、パース位置が巻き戻る
+          const remainder = afterString[0] ?? '';
+          outEndPos[0] = i + numericSlice.length - remainder.length;
           return new JsonFloat(f);
         }
         case '"':