Answer in brief
CVE-2026-23439 records a Medium severity (CVSS 5.5) vulnerability in udp_tunnel: fix NULL deref caused by udp_sock_create6 when CONFIG_IPV6=n. The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic), Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (generic), Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (generic) and additional mapped packages. Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
Answer in brief
CVE-2026-23439 records a Medium severity (CVSS 5.5) vulnerability in udp_tunnel: fix NULL deref caused by udp_sock_create6 when CONFIG_IPV6=n. The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic), Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (generic), Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (generic) and additional mapped packages. Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 5.5. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Linux/Linux (generic), Linux/Linux (generic), Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (generic), Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (generic) and additional mapped packages. Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| Linux/Linuxgeneric | >=fd384412e199b62c3ddaabd18dce86d0e164c5b9 <dfc96ae0074cc47b5478a59e5aa19233e434243f || >=fd384412e199b62c3ddaabd18dce86d0e164c5b9 <66117dbb3dbae82f86735bf727b1d59cc677afa1 || >=fd384412e199b62c3ddaabd18dce86d0e164c5b9 <ba7c9ddcdd077942b798979edb035207374d4096 || >=fd384412e199b62c3ddaabd18dce86d0e164c5b9 <a05a2149386f6dfb4245f522acdbef892acafc84 || >=fd384412e199b62c3ddaabd18dce86d0e164c5b9 <9f036aa0fe46c19e938f03d10e02c23f4fffae5e || >=fd384412e199b62c3ddaabd18dce86d0e164c5b9 <003343985f26dfefd0c94b1fe1316a2de74428b9 || >=fd384412e199b62c3ddaabd18dce86d0e164c5b9 <12aa4b73a67d95bc739995a2d6943aec2f9785c9 || >=fd384412e199b62c3ddaabd18dce86d0e164c5b9 <b3a6df291fecf5f8a308953b65ca72b7fc9e015d | dfc96ae0074cc47b5478a59e5aa19233e434243f, 66117dbb3dbae82f86735bf727b1d59cc677afa1, ba7c9ddcdd077942b798979edb035207374d4096, a05a2149386f6dfb4245f522acdbef892acafc84, 9f036aa0fe46c19e938f03d10e02c23f4fffae5e, 003343985f26dfefd0c94b1fe1316a2de74428b9, 12aa4b73a67d95bc739995a2d6943aec2f9785c9, b3a6df291fecf5f8a308953b65ca72b7fc9e015d |
| Linux/Linuxgeneric | 3.18 | Not reported |
| Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFPgeneric | >=V3.1.6 <* | * |
| Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFPgeneric | >=V3.1.5 <* | * |
| Siemens/SIMATIC S7-1500 CPU 1518F-4 PN/DP MFPgeneric | >=V3.1.6 <* | * |
| Siemens/SIMATIC S7-1500 CPU 1518F-4 PN/DP MFPgeneric | >=V3.1.5 <* | * |
| Siemens/SIPLUS S7-1500 CPU 1518-4 PN/DP MFPgeneric | >=V3.1.6 <* | * |
| Siemens/SIPLUS S7-1500 CPU 1518-4 PN/DP MFPgeneric | >=V3.1.5 <* | * |
Published upstream
Apr 3, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Jul 14, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Jul 14, 2026
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.
Quoted source text, attributed separately from HOL analysis.
CVSS is 5.5. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Linux/Linux (generic), Linux/Linux (generic), Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (generic), Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (generic) and additional mapped packages. Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| Linux/Linuxgeneric | >=fd384412e199b62c3ddaabd18dce86d0e164c5b9 <dfc96ae0074cc47b5478a59e5aa19233e434243f || >=fd384412e199b62c3ddaabd18dce86d0e164c5b9 <66117dbb3dbae82f86735bf727b1d59cc677afa1 || >=fd384412e199b62c3ddaabd18dce86d0e164c5b9 <ba7c9ddcdd077942b798979edb035207374d4096 || >=fd384412e199b62c3ddaabd18dce86d0e164c5b9 <a05a2149386f6dfb4245f522acdbef892acafc84 || >=fd384412e199b62c3ddaabd18dce86d0e164c5b9 <9f036aa0fe46c19e938f03d10e02c23f4fffae5e || >=fd384412e199b62c3ddaabd18dce86d0e164c5b9 <003343985f26dfefd0c94b1fe1316a2de74428b9 || >=fd384412e199b62c3ddaabd18dce86d0e164c5b9 <12aa4b73a67d95bc739995a2d6943aec2f9785c9 || >=fd384412e199b62c3ddaabd18dce86d0e164c5b9 <b3a6df291fecf5f8a308953b65ca72b7fc9e015d | dfc96ae0074cc47b5478a59e5aa19233e434243f, 66117dbb3dbae82f86735bf727b1d59cc677afa1, ba7c9ddcdd077942b798979edb035207374d4096, a05a2149386f6dfb4245f522acdbef892acafc84, 9f036aa0fe46c19e938f03d10e02c23f4fffae5e, 003343985f26dfefd0c94b1fe1316a2de74428b9, 12aa4b73a67d95bc739995a2d6943aec2f9785c9, b3a6df291fecf5f8a308953b65ca72b7fc9e015d |
| Linux/Linuxgeneric | 3.18 | Not reported |
| Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFPgeneric | >=V3.1.6 <* | * |
| Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFPgeneric | >=V3.1.5 <* | * |
| Siemens/SIMATIC S7-1500 CPU 1518F-4 PN/DP MFPgeneric | >=V3.1.6 <* | * |
| Siemens/SIMATIC S7-1500 CPU 1518F-4 PN/DP MFPgeneric | >=V3.1.5 <* | * |
| Siemens/SIPLUS S7-1500 CPU 1518-4 PN/DP MFPgeneric | >=V3.1.6 <* | * |
| Siemens/SIPLUS S7-1500 CPU 1518-4 PN/DP MFPgeneric | >=V3.1.5 <* | * |
Published upstream
Apr 3, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Jul 14, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Jul 14, 2026
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.
Quoted source text, attributed separately from HOL analysis.