diff --git a/.changeset/sentinel-dos-fix.md b/.changeset/sentinel-dos-fix.md
new file mode 100644
index 00000000..59373def
--- /dev/null
+++ b/.changeset/sentinel-dos-fix.md
@@ -0,0 +1,5 @@
+---
+"node-version": patch
+---
+
+Security: Fix potential DoS vulnerability by limiting maximum version string length to 256 characters.
diff --git a/src/index.ts b/src/index.ts
index 625ca808..297eb4dd 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -19,6 +19,11 @@ export const EOL_DATES: Record<string, string> = {
     "24": "2028-04-30",
 };
 
+/**
+ * Maximum allowed length for a version string to prevent DoS attacks.
+ */
+const MAX_VERSION_LENGTH = 256;
+
 /**
  * Check if a major version is EOL.
  */
@@ -52,6 +57,11 @@ export const getVersion = (): NodeVersion => {
      * Compare the current node version with a target version string.
      */
     const compareTo = (target: string): number => {
+        // Fail fast for excessively long strings to prevent DoS
+        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 b5942fd7..61c4b91a 100644
--- a/src/security.test.ts
+++ b/src/security.test.ts
@@ -63,4 +63,36 @@ describe("security fixes", () => {
         const v = getVersion();
         expect(v.isAtLeast("10.0.0")).toBe(true);
     });
+
+    describe("DoS prevention", () => {
+        test("should handle extremely long version strings gracefully", () => {
+            const v = getVersion();
+
+            // Generate a 1MB string
+            const hugeString = "1".repeat(1024 * 1024);
+
+            const start = performance.now();
+            const result = v.isAtLeast(hugeString);
+            const end = performance.now();
+
+            // Should return false (invalid version because it exceeds MAX_VERSION_LENGTH)
+            expect(result).toBe(false);
+
+            // Should execute quickly (under 50ms implies it didn't try to parse the whole thing)
+            expect(end - start).toBeLessThan(100);
+        });
+
+        test("should handle huge string with many dots", () => {
+            const v = getVersion();
+            const hugeDots = "1.".repeat(500000); // 1MB string with 500k dots
+
+            const start = performance.now();
+            const result = v.isAtLeast(hugeDots);
+            const end = performance.now();
+
+            expect(result).toBe(false);
+            // This is the critical check - without length limit this could be slow/OOM
+            expect(end - start).toBeLessThan(100);
+        });
+    });
 });