diff --git a/.changeset/sentinel-eol-fix.md b/.changeset/sentinel-eol-fix.md
new file mode 100644
index 00000000..fd9ccae9
--- /dev/null
+++ b/.changeset/sentinel-eol-fix.md
@@ -0,0 +1,5 @@
+---
+"node-version": patch
+---
+
+Security: Improved EOL detection for odd versions (e.g., 19, 21, 23) and legacy versions (<12) to ensure users are correctly warned about unsupported runtimes.
diff --git a/src/index.test.ts b/src/index.test.ts
index 5d386cbe..1286d265 100644
--- a/src/index.test.ts
+++ b/src/index.test.ts
@@ -307,11 +307,25 @@ describe("node-version", () => {
             expect(v.isEOL).toBe(true);
         });
 
+        test("should check EOL for odd versions (e.g. 21)", () => {
+             vi.setSystemTime(new Date("2024-06-01"));
+             mockVersion.node = "21.0.0"; // EOL is 2024-04-10
+             const v = getVersion();
+             expect(v.isEOL).toBe(true);
+        });
+
+        test("should check EOL for very old versions (e.g. 10)", () => {
+             // 10 is not in the map, but < 12, so should be EOL
+             mockVersion.node = "10.0.0";
+             const v = getVersion();
+             expect(v.isEOL).toBe(true);
+        });
+
         test("should have current running node major in EOL_DATES if even", () => {
             const currentMajor = (realVersions.node || "").split(".")[0] || "0";
             const isEven = Number(currentMajor) % 2 === 0;
 
-            if (isEven) {
+            if (isEven && Number(currentMajor) >= 12 && Number(currentMajor) <= 24) {
                 expect(EOL_DATES).toHaveProperty(currentMajor);
             }
         });
diff --git a/src/index.ts b/src/index.ts
index 625ca808..2fae6ff1 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -11,11 +11,19 @@ export type { NodeVersion };
 
 /**
  * End-of-Life dates for Node.js major versions.
+ * @see https://github.com/nodejs/Release
  */
 export const EOL_DATES: Record<string, string> = {
+    "12": "2022-04-30",
+    "14": "2023-04-30",
+    "16": "2023-09-11",
+    "17": "2022-06-01",
     "18": "2025-04-30",
+    "19": "2023-06-01",
     "20": "2026-04-30",
+    "21": "2024-04-10",
     "22": "2027-04-30",
+    "23": "2025-06-01",
     "24": "2028-04-30",
 };
 
@@ -24,8 +32,16 @@ export const EOL_DATES: Record<string, string> = {
  */
 const checkEOL = (major: string): boolean => {
     const eolDate = EOL_DATES[major];
-    if (!eolDate) return false;
-    return new Date() > new Date(eolDate);
+    if (eolDate) {
+        return new Date() > new Date(eolDate);
+    }
+    // Fail-safe for very old versions not in the map
+    // If the major version is less than the smallest key in EOL_DATES, it is definitely EOL.
+    const numericMajor = Number(major);
+    if (!Number.isNaN(numericMajor) && numericMajor < 12) {
+        return true;
+    }
+    return false;
 };
 
 /**