{"id":"CVE-2026-23439","summary":"udp_tunnel: fix NULL deref caused by udp_sock_create6 when CONFIG_IPV6=n","details":"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 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    \u003cTASK\u003e\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.","modified":"2026-04-19T04:18:03.475440Z","published":"2026-04-03T15:15:23.734Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/23xxx/CVE-2026-23439.json","cna_assigner":"Linux"},"references":[{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"},{"type":"WEB","url":"https://git.kernel.org/stable/c/003343985f26dfefd0c94b1fe1316a2de74428b9"},{"type":"WEB","url":"https://git.kernel.org/stable/c/12aa4b73a67d95bc739995a2d6943aec2f9785c9"},{"type":"WEB","url":"https://git.kernel.org/stable/c/66117dbb3dbae82f86735bf727b1d59cc677afa1"},{"type":"WEB","url":"https://git.kernel.org/stable/c/9f036aa0fe46c19e938f03d10e02c23f4fffae5e"},{"type":"WEB","url":"https://git.kernel.org/stable/c/a05a2149386f6dfb4245f522acdbef892acafc84"},{"type":"WEB","url":"https://git.kernel.org/stable/c/b3a6df291fecf5f8a308953b65ca72b7fc9e015d"},{"type":"WEB","url":"https://git.kernel.org/stable/c/ba7c9ddcdd077942b798979edb035207374d4096"},{"type":"WEB","url":"https://git.kernel.org/stable/c/dfc96ae0074cc47b5478a59e5aa19233e434243f"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/23xxx/CVE-2026-23439.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-23439"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"fd384412e199b62c3ddaabd18dce86d0e164c5b9"},{"fixed":"dfc96ae0074cc47b5478a59e5aa19233e434243f"},{"fixed":"66117dbb3dbae82f86735bf727b1d59cc677afa1"},{"fixed":"ba7c9ddcdd077942b798979edb035207374d4096"},{"fixed":"a05a2149386f6dfb4245f522acdbef892acafc84"},{"fixed":"9f036aa0fe46c19e938f03d10e02c23f4fffae5e"},{"fixed":"003343985f26dfefd0c94b1fe1316a2de74428b9"},{"fixed":"12aa4b73a67d95bc739995a2d6943aec2f9785c9"},{"fixed":"b3a6df291fecf5f8a308953b65ca72b7fc9e015d"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-23439.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"3.18.0"},{"fixed":"5.10.253"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.11.0"},{"fixed":"5.15.203"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.16.0"},{"fixed":"6.1.167"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.2.0"},{"fixed":"6.6.130"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.78"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.20"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"6.19.10"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-23439.json"}}],"schema_version":"1.7.5"}