core/types: sanity check the basefee length inside a header (#23171)

core/types/block.go

@@ -129,6 +129,11 @@ func (h *Header) SanityCheck() error {
 	if eLen := len(h.Extra); eLen > 100*1024 {
 		return fmt.Errorf("too large block extradata: size %d", eLen)
 	}
+	if h.BaseFee != nil {
+		if bfLen := h.BaseFee.BitLen(); bfLen > 256 {
+			return fmt.Errorf("too large base fee: bitlen %d", bfLen)
+		}
+	}
 	return nil
 }