diff --git a/src/mms/iso_cotp/cotp.c b/src/mms/iso_cotp/cotp.c
index cbb34b36..8c37d262 100644
--- a/src/mms/iso_cotp/cotp.c
+++ b/src/mms/iso_cotp/cotp.c
@@ -720,6 +720,9 @@ CotpConnection_readToTpktBuffer(CotpConnection* self)
             goto exit_waiting;
     }
 
+    if (self->packetSize <= bufPos)
+        goto exit_error;
+
     readBytes = readFromSocket(self, buffer + bufPos, self->packetSize - bufPos);
 
     if (readBytes < 0)