CVE-2026-23439

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: udp_tunnel: fix NULL deref caused by udp_sock_create6 when CONFIG_IPV6=n When CONFIG_IPV6 is disabled, the udp_sock_create6() function returns 0 (success) without actually creating a socket. Callers such as fou_create() then proceed to dereference the uninitialized socket pointer, resulting in a NULL pointer dereference. The captured NULL deref crash: BUG: kernel NULL pointer dereference, address: 0000000000000018 RIP: 0010:fou_nl_add_doit (net/ipv4/fou_core.c:590 net/ipv4/fou_core.c:764) [...] Call Trace: <TASK> genl_family_rcv_msg_doit.constprop.0 (net/netlink/genetlink.c:1114) genl_rcv_msg (net/netlink/genetlink.c:1194 net/netlink/genetlink.c:1209) [...] netlink_rcv_skb (net/netlink/af_netlink.c:2550) genl_rcv (net/netlink/genetlink.c:1219) netlink_unicast (net/netlink/af_netlink.c:1319 net/netlink/af_netlink.c:1344) netlink_sendmsg (net/netlink/af_netlink.c:1894) __sock_sendmsg (net/socket.c:727 (discriminator 1) net/socket.c:742 (discriminator 1)) __sys_sendto (./include/linux/file.h:62 (discriminator 1) ./include/linux/file.h:83 (discriminator 1) net/socket.c:2183 (discriminator 1)) __x64_sys_sendto (net/socket.c:2213 (discriminator 1) net/socket.c:2209 (discriminator 1) net/socket.c:2209 (discriminator 1)) do_syscall_64 (arch/x86/entry/syscall_64.c:63 (discriminator 1) arch/x86/entry/syscall_64.c:94 (discriminator 1)) entry_SYSCALL_64_after_hwframe (net/arch/x86/entry/entry_64.S:130) This patch makes udp_sock_create6 return -EPFNOSUPPORT instead, so callers correctly take their error paths. There is only one caller of the vulnerable function and only privileged users can trigger it.

CVSS Score

Affected Products

Related Weaknesses (CWE)

References

• https://git.kernel.org/stable/c/003343985f26dfefd0c94b1fe1316a2de74428b9Patch
• https://git.kernel.org/stable/c/12aa4b73a67d95bc739995a2d6943aec2f9785c9Patch
• https://git.kernel.org/stable/c/66117dbb3dbae82f86735bf727b1d59cc677afa1Patch
• https://git.kernel.org/stable/c/9f036aa0fe46c19e938f03d10e02c23f4fffae5ePatch
• https://git.kernel.org/stable/c/a05a2149386f6dfb4245f522acdbef892acafc84Patch
• https://git.kernel.org/stable/c/b3a6df291fecf5f8a308953b65ca72b7fc9e015dPatch
• https://git.kernel.org/stable/c/ba7c9ddcdd077942b798979edb035207374d4096Patch
• https://git.kernel.org/stable/c/dfc96ae0074cc47b5478a59e5aa19233e434243fPatch