{"id":"CVE-2026-23439","title":"udp_tunnel: fix NULL deref caused by udp_sock_create6 when CONFIG_IPV6=n","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nudp_tunnel: fix NULL deref caused by udp_sock_create6 when CONFIG_IPV6=n\n\nWhen CONFIG_IPV6 is disabled, the udp_sock_create6() function returns 0\n(success) without actu…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= fd384412e199b62c3ddaabd18dce86d0e164c5b9 < dfc96ae0074cc47b5478a59e5aa19233e434243f","Linux >= fd384412e199b62c3ddaabd18dce86d0e164c5b9 < 66117dbb3dbae82f86735bf727b1d59cc677afa1","Linux >= fd384412e199b62c3ddaabd18dce86d0e164c5b9 < ba7c9ddcdd077942b798979edb035207374d4096","Linux >= fd384412e199b62c3ddaabd18dce86d0e164c5b9 < a05a2149386f6dfb4245f522acdbef892acafc84","Linux >= fd384412e199b62c3ddaabd18dce86d0e164c5b9 < 9f036aa0fe46c19e938f03d10e02c23f4fffae5e","Linux >= fd384412e199b62c3ddaabd18dce86d0e164c5b9 < 003343985f26dfefd0c94b1fe1316a2de74428b9","Linux >= fd384412e199b62c3ddaabd18dce86d0e164c5b9 < 12aa4b73a67d95bc739995a2d6943aec2f9785c9","Linux >= fd384412e199b62c3ddaabd18dce86d0e164c5b9 < b3a6df291fecf5f8a308953b65ca72b7fc9e015d","Linux 3.18"],"published":"2026-04-03","updated":"2026-09-08","sourceUpdated":"2026-09-08T08:46:12.477Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-23439","references":[{"url":"https://git.kernel.org/stable/c/dfc96ae0074cc47b5478a59e5aa19233e434243f"},{"url":"https://git.kernel.org/stable/c/66117dbb3dbae82f86735bf727b1d59cc677afa1"},{"url":"https://git.kernel.org/stable/c/ba7c9ddcdd077942b798979edb035207374d4096"},{"url":"https://git.kernel.org/stable/c/a05a2149386f6dfb4245f522acdbef892acafc84"},{"url":"https://git.kernel.org/stable/c/9f036aa0fe46c19e938f03d10e02c23f4fffae5e"},{"url":"https://git.kernel.org/stable/c/003343985f26dfefd0c94b1fe1316a2de74428b9"},{"url":"https://git.kernel.org/stable/c/12aa4b73a67d95bc739995a2d6943aec2f9785c9"},{"url":"https://git.kernel.org/stable/c/b3a6df291fecf5f8a308953b65ca72b7fc9e015d"}],"tags":["cve.org"],"epss":0.00129,"epssPercentile":0.02085,"ingestedAt":"2026-09-08T15:33:26.992Z","slug":"CVE-2026-23439","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nudp_tunnel: fix NULL deref caused by udp_sock_create6 when CONFIG_IPV6=n\n\nWhen CONFIG_IPV6 is disabled, the udp_sock_create6() function returns 0\n(success) without actually creating a socket. Callers such as\nfou_create() then proceed to dereference the uninitialized socket\npointer, resulting in a NULL pointer dereference.\n\nThe captured NULL deref crash:\n  BUG: kernel NULL pointer dereference, address: 0000000000000018\n  RIP: 0010:fou_nl_add_doit (net/ipv4/fou_core.c:590 net/ipv4/fou_core.c:764)\n  [...]\n  Call Trace:\n    <TASK>\n    genl_family_rcv_msg_doit.constprop.0 (net/netlink/genetlink.c:1114)\n    genl_rcv_msg (net/netlink/genetlink.c:1194 net/netlink/genetlink.c:1209)\n    [...]\n    netlink_rcv_skb (net/netlink/af_netlink.c:2550)\n    genl_rcv (net/netlink/genetlink.c:1219)\n    netlink_unicast (net/netlink/af_netlink.c:1319 net/netlink/af_netlink.c:1344)\n    netlink_sendmsg (net/netlink/af_netlink.c:1894)\n    __sock_sendmsg (net/socket.c:727 (discriminator 1) net/socket.c:742 (discriminator 1))\n    __sys_sendto (./include/linux/file.h:62 (discriminator 1) ./include/linux/file.h:83 (discriminator 1) net/socket.c:2183 (discriminator 1))\n    __x64_sys_sendto (net/socket.c:2213 (discriminator 1) net/socket.c:2209 (discriminator 1) net/socket.c:2209 (discriminator 1))\n    do_syscall_64 (arch/x86/entry/syscall_64.c:63 (discriminator 1) arch/x86/entry/syscall_64.c:94 (discriminator 1))\n    entry_SYSCALL_64_after_hwframe (net/arch/x86/entry/entry_64.S:130)\n\nThis patch makes udp_sock_create6 return -EPFNOSUPPORT instead, so\ncallers correctly take their error paths. There is only one caller of\nthe vulnerable function and only privileged users can trigger it.\n\n## Affected\n\n- `Linux >= fd384412e199b62c3ddaabd18dce86d0e164c5b9 < dfc96ae0074cc47b5478a59e5aa19233e434243f`\n- `Linux >= fd384412e199b62c3ddaabd18dce86d0e164c5b9 < 66117dbb3dbae82f86735bf727b1d59cc677afa1`\n- `Linux >= fd384412e199b62c3ddaabd18dce86d0e164c5b9 < ba7c9ddcdd077942b798979edb035207374d4096`\n- `Linux >= fd384412e199b62c3ddaabd18dce86d0e164c5b9 < a05a2149386f6dfb4245f522acdbef892acafc84`\n- `Linux >= fd384412e199b62c3ddaabd18dce86d0e164c5b9 < 9f036aa0fe46c19e938f03d10e02c23f4fffae5e`\n- `Linux >= fd384412e199b62c3ddaabd18dce86d0e164c5b9 < 003343985f26dfefd0c94b1fe1316a2de74428b9`\n- `Linux >= fd384412e199b62c3ddaabd18dce86d0e164c5b9 < 12aa4b73a67d95bc739995a2d6943aec2f9785c9`\n- `Linux >= fd384412e199b62c3ddaabd18dce86d0e164c5b9 < b3a6df291fecf5f8a308953b65ca72b7fc9e015d`\n- `Linux 3.18`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}