CVE-2025-21636 is a medium-severity vulnerability in the Linux kernel SCTP sysctl implementation related to the plpmtud_probe_interval parameter. The issue arises from improper use of the current->nsproxy pointer, which can be NULL in some cases, leading to a null pointer dereference and kernel crash (Oops). The vulnerability has been addressed by changing the code to avoid using current->nsproxy and instead obtaining the 'net' structure from a safer source.