CVE-2023-54142: 
Linux Kernel vulnerability analysis and mitigation

CVE-2023-54142 is a use-after-free vulnerability in the Linux kernel's GTP (GPRS Tunneling Protocol) implementation, specifically within the __gtp_encap_destroy() function. The flaw was introduced by commit e198987e7dd7 ("gtp: fix suspicious RCU usage"), which added lock_sock() and release_sock() calls to protect sk->sk_user_data, but incorrectly calls release_sock() after sock_put() has already released the last reference count on the socket, resulting in a freed socket being accessed. The vulnerability was discovered via syzkaller, a kernel fuzzing tool, and publicly disclosed on December 24, 2025. It affects the Linux kernel and has been assigned a medium severity estimate with an EPSS score of 0.033% (Red Hat CVE, Feedly).

The root cause is a use-after-free (CWE-416) in the __gtp_encap_destroy() function of the Linux kernel's GTP network driver. When the function calls sock_put() to release the last reference to the socket (sk), the socket memory is freed; however, release_sock() is subsequently called on the now-freed socket object, causing an illegal memory access. The syzkaller-reported KASAN trace shows a slab-use-after-free write of size 4 during a spin lock acquisition (_raw_spin_lock_bh) on the freed socket address, triggered by the same process that freed it. The fix involves reordering the release_sock() call to occur before sock_put(), ensuring the socket is not accessed after its reference count reaches zero (Red Hat CVE, Feedly).

Successful exploitation of this vulnerability could lead to kernel memory corruption, potentially resulting in system crashes (denial of service), unauthorized memory access, or in more severe scenarios, arbitrary code execution in kernel context. The vulnerability affects the GTP network subsystem, which is relevant to systems running mobile core network components (e.g., 4G/5G infrastructure using GPRS tunneling). Lateral movement or privilege escalation within the kernel is theoretically possible if an attacker can reliably control the use-after-free condition (Red Hat CVE, Feedly).

The primary remediation is to update to a patched Linux kernel version that includes the fix for __gtp_encap_destroy() (reordering release_sock() before sock_put()). Patches have been submitted to the stable kernel tree (commits 9c9662e2512b, 17d6b6354f00, 58fa341327fd, bccc7ace12e6). Red Hat has tracked this via Bugzilla bug #2425205 and SUSE has issued kernel security updates addressing this CVE. If immediate patching is not feasible, consider disabling GTP kernel module support (modprobe -r gtp) if GTP tunneling is not required in your environment (Red Hat CVE, Feedly).