CVE-2026-43120 is a high-severity vulnerability in the Linux kernel's RDMA/irdma subsystem involving a double free condition during memory region re-registration. The flaw occurs when the IB_MR_REREG_TRANS flag is set and a failure happens after allocating a new user memory region (umem), leading to a stale pointer that causes a double free when the user calls deregistration. This can result in memory corruption with potential confidentiality, integrity, and availability impacts. The issue has been fixed by setting the pointer to NULL after releasing the umem to prevent double free.