That CLA grants HashiCorp full license over your Copyright, and explicitly allows them to sublicense your contributions[1]. Drew Devault's blog posts[2][3] on this topic are extremely relevant.
[1] > Grant of Copyright License. Subject to the terms and conditions of this Agreement, You hereby grant to HashiCorp and to recipients of software distributed by HashiCorp a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable copyright license to reproduce, prepare derivative works of, publicly display, publicly perform, sublicense, and distribute Your Contributions and such derivative works.
[2] https://drewdevault.com/2018/10/05/Dont-sign-a-CLA.html
[3] https://drewdevault.com/2023/07/04/Dont-sign-a-CLA-2.html