CDR is a default file format of CorelDRAW so in theory, you need CorelDRAW to open it. There are some vector graphics software that has a compatibility with CorelDRAW to allow you to open a CDR file without CorelDRAW. One of which is Inkscape.
If you are unable to open a CDR file, it may be because it got corrupted or damaged. In this case, the CorelDraw recovery tool will help you fix the problems and restore your projects and drawings.
Inkscape is an open source vector graphics software that is available for all major desktop operating systems: Windows, Linux, and macOS. It has a default file format of SVG but also recognizes vector formats created by proprietary graphics software such as CDR and AI (Adobe Illustrator). You can download Inkscape on its official website. If you use Ubuntu, you can also install Inkscape via Ubuntu Software Center and if you use Windows 10, Inkscape is also available in Microsoft Store.
To open a CDR file with Inkscape, simply launch the Inkscape app once it is installed on your computer. Go to File -> Open (Ctrl+O) and select the CDR file you want to open and click the Open button.
Inkscape will convert your CDR file into an editable format on its app so you can edit your CDR file. Here is the example of a CDR file opened with Inkscape.
For the first operation, you can try to select a certain part of the image using a path tool or ungroup a certain region of the image.
In addition to Inkscape, another tool that you can use to open and edit a CDR file without CorelDRAW is LibreOffice Draw. It is also free and available for Windows, Linux, and macOS.