diff --git a/src/crypto/tls/handshake_messages.go b/src/crypto/tls/handshake_messages.go
index ad3e5fa352f..d9a475aab14 100644
--- a/src/crypto/tls/handshake_messages.go
+++ b/src/crypto/tls/handshake_messages.go
@@ -1790,7 +1790,7 @@ func (m *certificateRequestMsg) unmarshal(data []byte) bool {
 		}
 		sigAndHashLen := uint16(data[0])<<8 | uint16(data[1])
 		data = data[2:]
-		if sigAndHashLen&1 != 0 {
+		if sigAndHashLen&1 != 0 || sigAndHashLen == 0 {
 			return false
 		}
 		if len(data) < int(sigAndHashLen) {