mse/mse.go | 4 ++++

diff --git a/mse/mse.go b/mse/mse.go
index 421ade3fcba6813fee2bf5113264c6044bb30d5f..eb2480aaccf7247e2076276f7a6e8546907c6a68 100644
--- a/mse/mse.go
+++ b/mse/mse.go
@@ -366,6 +366,10 @@ 	h.postWrite(xor(hash(req2, h.skey), hash(req3, h.s[:])))
 	buf := &bytes.Buffer{}
 	padLen := uint16(newPadLen())
 	err = marshal(buf, vc[:], uint32(cryptoMethodRC4), padLen, zeroPad[:padLen], uint16(len(h.ia)), h.ia)
+	if len(h.ia) > math.MaxUint16 {
+		err = errors.New("initial payload too large")
+		return
+	}
 	if err != nil {
 		return
 	}