diff --git a/Foundation/org.egovframe.rte.fdl.string/src/main/java/org/egovframe/rte/fdl/string/EgovStringUtil.java b/Foundation/org.egovframe.rte.fdl.string/src/main/java/org/egovframe/rte/fdl/string/EgovStringUtil.java
index d3db1630..0498ba31 100755
--- a/Foundation/org.egovframe.rte.fdl.string/src/main/java/org/egovframe/rte/fdl/string/EgovStringUtil.java
+++ b/Foundation/org.egovframe.rte.fdl.string/src/main/java/org/egovframe/rte/fdl/string/EgovStringUtil.java
@@ -282,6 +282,13 @@ public static String toSubString(String source, int beginIndex) {
      * search
      */
     public static int search(String source, String target) {
+        // source 또는 target이 null/빈 문자열이면 셀 대상이 없으므로 0을 반환한다.
+        // 특히 target이 빈 문자열이면 indexOf("")가 항상 0을 반환해
+        // i가 0에 고정되어 무한 루프에 빠지므로 반드시 먼저 걸러낸다.
+        if (source == null || source.isEmpty() || target == null || target.isEmpty()) {
+            return 0;
+        }
+
         int result = 0;
         String strCheck = source;
         for (int i = 0; i < source.length(); ) {
diff --git a/Foundation/org.egovframe.rte.fdl.string/src/test/java/org/egovframe/rte/fdl/string/EgovStringUtilTest.java b/Foundation/org.egovframe.rte.fdl.string/src/test/java/org/egovframe/rte/fdl/string/EgovStringUtilTest.java
index 6ce10bee..7090a8f9 100755
--- a/Foundation/org.egovframe.rte.fdl.string/src/test/java/org/egovframe/rte/fdl/string/EgovStringUtilTest.java
+++ b/Foundation/org.egovframe.rte.fdl.string/src/test/java/org/egovframe/rte/fdl/string/EgovStringUtilTest.java
@@ -4,6 +4,7 @@
 import org.junit.jupiter.api.extension.ExtendWith;
 import org.springframework.test.context.junit.jupiter.SpringExtension;
 
+import java.time.Duration;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
@@ -406,4 +407,34 @@ public void testGetTokens() {
         assertEquals(4, EgovStringUtil.getTokens(str).size());
     }
 
+    /**
+     * search는 source 안에서 target이 나타나는 횟수를 센다.
+     */
+    @Test
+    public void testSearchCount() {
+        assertEquals(2, EgovStringUtil.search("aXbXc", "X"));
+        assertEquals(0, EgovStringUtil.search("abc", "z"));
+        assertEquals(2, EgovStringUtil.search("aaaa", "aa"));
+    }
+
+    /**
+     * target이 빈 문자열이면 indexOf("")가 항상 0을 반환해
+     * 기존 구현은 무한 루프에 빠졌다. 이제는 0을 반환해야 한다.
+     */
+    @Test
+    public void testSearchEmptyTargetDoesNotLoop() {
+        assertTimeoutPreemptively(Duration.ofSeconds(2),
+                () -> assertEquals(0, EgovStringUtil.search("abc", "")));
+    }
+
+    /**
+     * null 입력은 NPE 없이 0을 반환해야 한다.
+     */
+    @Test
+    public void testSearchNullInputs() {
+        assertEquals(0, EgovStringUtil.search(null, "a"));
+        assertEquals(0, EgovStringUtil.search("abc", null));
+        assertEquals(0, EgovStringUtil.search("", "a"));
+    }
+
 }