Try exploiting this CVE by studying some articles:
https://jfrog.com/blog/cve-2022-25845-analyzing-the-fastjson-auto-type-bypass-rce-vulnerability/
https://www.freebuf.com/vuls/339752.html
This is my analyze:
https://github.com/nerowander/CVE-2022-25845-exploit/blob/main/CVE-2022-25845.pdf