udp_tunnel: fix NULL deref caused by udp_sock_create6 when CONFIG_IPV6=n

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Summary

CVECVE-2026-23439
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-04-03 16:16:25 UTC
Updated2026-04-18 09:16:26 UTC
DescriptionIn 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.

Risk And Classification

EPSS: 0.000320000 probability, percentile 0.090980000 (date 2026-04-18)

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected fd384412e199b62c3ddaabd18dce86d0e164c5b9 dfc96ae0074cc47b5478a59e5aa19233e434243f git Not specified
CNA Linux Linux affected fd384412e199b62c3ddaabd18dce86d0e164c5b9 66117dbb3dbae82f86735bf727b1d59cc677afa1 git Not specified
CNA Linux Linux affected fd384412e199b62c3ddaabd18dce86d0e164c5b9 ba7c9ddcdd077942b798979edb035207374d4096 git Not specified
CNA Linux Linux affected fd384412e199b62c3ddaabd18dce86d0e164c5b9 a05a2149386f6dfb4245f522acdbef892acafc84 git Not specified
CNA Linux Linux affected fd384412e199b62c3ddaabd18dce86d0e164c5b9 9f036aa0fe46c19e938f03d10e02c23f4fffae5e git Not specified
CNA Linux Linux affected fd384412e199b62c3ddaabd18dce86d0e164c5b9 003343985f26dfefd0c94b1fe1316a2de74428b9 git Not specified
CNA Linux Linux affected fd384412e199b62c3ddaabd18dce86d0e164c5b9 12aa4b73a67d95bc739995a2d6943aec2f9785c9 git Not specified
CNA Linux Linux affected fd384412e199b62c3ddaabd18dce86d0e164c5b9 b3a6df291fecf5f8a308953b65ca72b7fc9e015d git Not specified
CNA Linux Linux affected 3.18 Not specified
CNA Linux Linux unaffected 3.18 semver Not specified
CNA Linux Linux unaffected 5.10.253 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.203 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.167 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.130 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.78 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.20 6.18.* semver Not specified
CNA Linux Linux unaffected 6.19.10 6.19.* semver Not specified
CNA Linux Linux unaffected 7.0 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/b3a6df291fecf5f8a308953b65ca72b7fc9e015d 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/dfc96ae0074cc47b5478a59e5aa19233e434243f 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/9f036aa0fe46c19e938f03d10e02c23f4fffae5e 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/ba7c9ddcdd077942b798979edb035207374d4096 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/003343985f26dfefd0c94b1fe1316a2de74428b9 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/12aa4b73a67d95bc739995a2d6943aec2f9785c9 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/a05a2149386f6dfb4245f522acdbef892acafc84 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/66117dbb3dbae82f86735bf727b1d59cc677afa1 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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