{"id":"CVE-2026-23439","title":"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…","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":"medium","cvss":5.5,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","cwe":["CWE-476"],"vendor":"linux","product":"linux_kernel","affected":["linux_kernel >= 3.18.1, < 5.10.253","linux_kernel >= 5.11, < 5.15.203","linux_kernel >= 5.16, < 6.1.167","linux_kernel >= 6.2, < 6.6.130","linux_kernel >= 6.7, < 6.12.78","linux_kernel >= 6.13, < 6.18.20","linux_kernel >= 6.19, < 6.19.10","linux_kernel = 3.18","linux_kernel = 7.0"],"patched":["linux_kernel 6.19.10"],"published":"2026-04-03","updated":"2026-10-15","sourceUpdated":"2026-10-15T02:18:56.773","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-23439","references":[{"url":"https://git.kernel.org/stable/c/003343985f26dfefd0c94b1fe1316a2de74428b9","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/12aa4b73a67d95bc739995a2d6943aec2f9785c9","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/66117dbb3dbae82f86735bf727b1d59cc677afa1","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/9f036aa0fe46c19e938f03d10e02c23f4fffae5e","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/a05a2149386f6dfb4245f522acdbef892acafc84","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/b3a6df291fecf5f8a308953b65ca72b7fc9e015d","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/ba7c9ddcdd077942b798979edb035207374d4096","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/dfc96ae0074cc47b5478a59e5aa19233e434243f","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://cert-portal.siemens.com/productcert/html/ssa-019113.html","label":"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"},{"url":"https://cert-portal.siemens.com/productcert/html/ssa-082556.html","label":"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"},{"url":"https://cert-portal.siemens.com/productcert/html/ssa-457936.html","label":"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"}],"tags":["nvd","cve.org"],"epss":0.00129,"epssPercentile":0.02502,"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_kernel >= 3.18.1, < 5.10.253`\n- `linux_kernel >= 5.11, < 5.15.203`\n- `linux_kernel >= 5.16, < 6.1.167`\n- `linux_kernel >= 6.2, < 6.6.130`\n- `linux_kernel >= 6.7, < 6.12.78`\n- `linux_kernel >= 6.13, < 6.18.20`\n- `linux_kernel >= 6.19, < 6.19.10`\n- `linux_kernel = 3.18`\n- `linux_kernel = 7.0`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `linux_kernel 6.19.10`","depth":"sunlit","depthScore":30,"depthScoreParts":{"impact":30.3,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[{"seq":221685,"id":"CVE-2026-23439","ts":1792035320407,"field":"cvss","old":null,"new":"5.5"},{"seq":221684,"id":"CVE-2026-23439","ts":1792035320407,"field":"severity","old":"none","new":"medium"}]}