nodejs
diff --git a/‎src/string_bytes.cc‎
Lines changed: 5 additions & 1 deletion b/‎src/string_bytes.cc‎
Lines changed: 5 additions & 1 deletion
diff --git a/‎test/parallel/test-buffer-write.js‎
Lines changed: 21 additions & 0 deletions b/‎test/parallel/test-buffer-write.js‎
Lines changed: 21 additions & 0 deletions
@@ -309,7 +309,11 @@ size_t StringBytes::WriteUCS2(char* buf,
                               size_t* chars_written) {
   uint16_t* const dst = reinterpret_cast<uint16_t*>(buf);
 
-  size_t max_chars = (buflen / sizeof(*dst));
+  size_t max_chars = buflen / sizeof(*dst);
+  if (max_chars == 0) {
+    return 0;
+  }
+
   size_t nchars;
   size_t alignment = reinterpret_cast<uintptr_t>(dst) % sizeof(*dst);
   if (alignment == 0) {
 
@@ -62,3 +62,24 @@ for (let i = 1; i < 10; i++) {
   assert.ok(!Buffer.isEncoding(encoding));
   assert.throws(() => Buffer.alloc(9).write('foo', encoding), error);
 }
+
+// UCS-2 overflow CVE-2018-12115
+for (let i = 1; i < 4; i++) {
+  // Allocate two Buffers sequentially off the pool. Run more than once in case
+  // we hit the end of the pool and don't get sequential allocations
+  const x = Buffer.allocUnsafe(4).fill(0);
+  const y = Buffer.allocUnsafe(4).fill(1);
+  // Should not write anything, pos 3 doesn't have enough room for a 16-bit char
+  assert.strictEqual(x.write('ыыыыыы', 3, 'ucs2'), 0);
+  // CVE-2018-12115 experienced via buffer overrun to next block in the pool
+  assert.strictEqual(Buffer.compare(y, Buffer.alloc(4, 1)), 0);
+}
+
+// Should not write any data when there is no space for 16-bit chars
+const z = Buffer.alloc(4, 0);
+assert.strictEqual(z.write('\u0001', 3, 'ucs2'), 0);
+assert.strictEqual(Buffer.compare(z, Buffer.alloc(4, 0)), 0);
+
+// Large overrun could corrupt the process
+assert.strictEqual(Buffer.alloc(4)
+  .write('ыыыыыы'.repeat(100), 3, 'utf16le'), 0);