diff --git a/src/extract.ts b/src/extract.ts
index 07c4472..1fd4814 100644
--- a/src/extract.ts
+++ b/src/extract.ts
@@ -41,6 +41,7 @@ export function extractZip(bytes: Buffer, targetDir: string): string[] {
   // A lemezre írás csak a teljes szűrés után történik, így ha valamelyik
   // korlát hibát dob, semmi nem kerül a célmappába.
   let total = 0;
+  const normalizedPaths: string[] = [];
   let entryCount = 0;
   const entries = unzipSync(new Uint8Array(bytes), {
     filter(info) {
@@ -58,9 +59,22 @@ export function extractZip(bytes: Buffer, targetDir: string): string[] {
       if (total > MAX_TOTAL_BYTES) {
         throw new Error("A zip kibontott mérete meghaladja a 200 MB-os korlátot.");
       }
+      normalizedPaths.push(
+        posix.normalize(info.name.replace(/\\/g, "/")).normalize("NFC").toLowerCase()
+      );
       return true;
     }
   });
+  const targets = new Set(normalizedPaths);
+  const nestedConflict = normalizedPaths.some((name) => {
+    for (let parent = posix.dirname(name); parent !== "."; parent = posix.dirname(parent)) {
+      if (targets.has(parent)) return true;
+    }
+    return false;
+  });
+  if (targets.size !== normalizedPaths.length || targets.has(".") || nestedConflict) {
+    throw new Error("Ütköző útvonalak a zipben, a kibontás leáll.");
+  }
   const written: string[] = [];
 
   for (const [name, data] of Object.entries(entries)) {
diff --git a/test/extract.test.ts b/test/extract.test.ts
index 52d9af8..13a29ff 100644
--- a/test/extract.test.ts
+++ b/test/extract.test.ts
@@ -74,6 +74,32 @@ function buildManyEntryZip(entryCount: number): Buffer {
 }
 
 describe("extractZip", () => {
+  it.each(
+    (
+      [
+        ["a", "a/b"],
+        ["A", "a"],
+        ["a/b", "a\\b"],
+        ["a/./b", "a/b"],
+        ["é", "e\u0301"]
+      ] as const
+    ).flatMap<[string, string]>(([a, b]) => [
+      [a, b],
+      [b, a]
+    ])
+  )("rejects conflicting %s and %s before writing", (a, b) => {
+    const tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), "tarhely-conflict-"));
+    try {
+      const zip = Buffer.from(
+        zipSync({ "safe.txt": Buffer.from("ok"), [a]: Buffer.from("a"), [b]: Buffer.from("b") })
+      );
+      expect(() => extractZip(zip, tmpDir)).toThrow("Ütköző útvonalak");
+      expect(fs.readdirSync(tmpDir)).toEqual([]);
+    } finally {
+      fs.rmSync(tmpDir, { recursive: true, force: true });
+    }
+  });
+
   it("extracts zip entries to target directory and returns relative paths", () => {
     const tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), "tarhely-test-"));
     const zipData = Buffer.from(