The Linux kernel contains a NULL pointer dereference in the address family iucv callback for handling SYN packets. When child socket allocation fails, the code unconditionally calls iucv_sock_kill() with a NULL parameter. iucv_sock_kill() immediately dereferences the socket pointer, causing a kernel crash. The confirmed impact is a denial‑of‑service that can bring the entire system down when the vulnerability is exercised.

All Linux distributions that ship a kernel version including the traditional iucv networking code and preceding the commit that introduced the fix are affected. No specific kernel version numbers are listed, so any kernel containing the pre‑patch code for afiucv_hs_callback_syn() is at risk.

The CVSS score of 7.5 reflects high severity. The EPSS score of < 1 % and lack of listing in the CISA KEV catalog indicate limited exploitation activity so far. The flaw causes an immediate kernel crash when a child socket allocation fails and the code path is exercised, potentially resulting in a denial‑of‑service that brings the entire system down. The likely attack vector is local or requires elevated privileges to initiate iucv connection attempts, so the risk is moderate to high for unpatched systems but remains limited until active exploitation surfaces.