In the Linux kernel, the following vulnerability has been resolved: netrom: fix double-free in nrrouteframe() In nrrouteframe(), oldskb is immediately freed without checking if nrneigh->ax25 pointer is NULL. Therefore, if nrneigh->ax25 is NULL, the caller function will free oldskb again, causing a double-free bug. Therefore, to prevent this, we need to modify it to check whether nrneigh->ax25 is NULL before freeing oldskb.