diff --git a/src/index.ts b/src/index.ts
index 625ca80..4985035 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -19,6 +19,12 @@ export const EOL_DATES: Record<string, string> = {
     "24": "2028-04-30",
 };
 
+/**
+ * Maximum allowed length for version strings.
+ * Used to prevent potential DoS attacks via extremely long input strings.
+ */
+const MAX_VERSION_LENGTH = 256;
+
 /**
  * Check if a major version is EOL.
  */
@@ -52,6 +58,10 @@ export const getVersion = (): NodeVersion => {
      * Compare the current node version with a target version string.
      */
     const compareTo = (target: string): number => {
+        if (target.length > MAX_VERSION_LENGTH) {
+            return NaN;
+        }
+
         if (target !== target.trim() || target.length === 0) {
             return NaN;
         }
diff --git a/src/security.test.ts b/src/security.test.ts
index b5942fd..2badf94 100644
--- a/src/security.test.ts
+++ b/src/security.test.ts
@@ -63,4 +63,12 @@ describe("security fixes", () => {
         const v = getVersion();
         expect(v.isAtLeast("10.0.0")).toBe(true);
     });
+
+    test("should reject extremely long version strings (DoS prevention)", () => {
+        const v = getVersion();
+        // 300 chars > MAX_VERSION_LENGTH (256)
+        const longString = "1".repeat(300);
+        expect(v.isAtLeast(longString)).toBe(false);
+        expect(v.isAtMost(longString)).toBe(false);
+    });
 });