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Fencer Vulns
high 7.5

CVE-2026-23003 json

ip6_tunnel: use skb_vlan_inet_prepare() in __ip6_tnl_rcv()

published 2026-01-25 9 mo ago modified 2026-10-19 20 d ago also EUVD-2026-4621

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 46%
public exploits
0
none known

Summary

In the Linux kernel, the following vulnerability has been resolved:

ip6_tunnel: use skb_vlan_inet_prepare() in __ip6_tnl_rcv()

Blamed commit did not take care of VLAN encapsulations as spotted by syzbot [1].

Use skb_vlan_inet_prepare() instead of pskb_inet_may_pull().

[1] BUG: KMSAN: uninit-value in __INET_ECN_decapsulate include/net/inet_ecn.h:253 [inline] BUG: KMSAN: uninit-value in INET_ECN_decapsulate include/net/inet_ecn.h:275 [inline] BUG: KMSAN: uninit-value in IP6_ECN_decapsulate+0x7a8/0x1fa0 include/net/inet_ecn.h:321 __INET_ECN_decapsulate include/net/inet_ecn.h:253 [inline] INET_ECN_decapsulate include/net/inet_ecn.h:275 [inline] IP6_ECN_decapsulate+0x7a8/0x1fa0 include/net/inet_ecn.h:321 ip6ip6_dscp_ecn_decapsulate+0x16f/0x1b0 net/ipv6/ip6_tunnel.c:729 __ip6_tnl_rcv+0xed9/0x1b50 net/ipv6/ip6_tunnel.c:860 ip6_tnl_rcv+0xc3/0x100 net/ipv6/ip6_tunnel.c:903 gre_rcv+0x1529/0x1b90 net/ipv6/ip6_gre.c:-1 ip6_protocol_deliver_rcu+0x1c89/0x2c60 net/ipv6/ip6_input.c:438 ip6_input_finish+0x1f4/0x4a0 net/ipv6/ip6_input.c:489 NF_HOOK include/linux/netfilter.h:318 [inline] ip6_input+0x9c/0x330 net/ipv6/ip6_input.c:500 ip6_mc_input+0x7ca/0xc10 net/ipv6/ip6_input.c:590 dst_input include/net/dst.h:474 [inline] ip6_rcv_finish+0x958/0x990 net/ipv6/ip6_input.c:79 NF_HOOK include/linux/netfilter.h:318 [inline] ipv6_rcv+0xf1/0x3c0 net/ipv6/ip6_input.c:311 __netif_receive_skb_one_core net/core/dev.c:6139 [inline] __netif_receive_skb+0x1df/0xac0 net/core/dev.c:6252 netif_receive_skb_internal net/core/dev.c:6338 [inline] netif_receive_skb+0x57/0x630 net/core/dev.c:6397 tun_rx_batched+0x1df/0x980 drivers/net/tun.c:1485 tun_get_user+0x5c0e/0x6c60 drivers/net/tun.c:1953 tun_chr_write_iter+0x3e9/0x5c0 drivers/net/tun.c:1999 new_sync_write fs/read_write.c:593 [inline] vfs_write+0xbe2/0x15d0 fs/read_write.c:686 ksys_write fs/read_write.c:738 [inline] __do_sys_write fs/read_write.c:749 [inline] __se_sys_write fs/read_write.c:746 [inline] __x64_sys_write+0x1fb/0x4d0 fs/read_write.c:746 x64_sys_call+0x30ab/0x3e70 arch/x86/include/generated/asm/syscalls_64.h:2 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xd3/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Uninit was created at: slab_post_alloc_hook mm/slub.c:4960 [inline] slab_alloc_node mm/slub.c:5263 [inline] kmem_cache_alloc_node_noprof+0x9e7/0x17a0 mm/slub.c:5315 kmalloc_reserve+0x13c/0x4b0 net/core/skbuff.c:586 __alloc_skb+0x805/0x1040 net/core/skbuff.c:690 alloc_skb include/linux/skbuff.h:1383 [inline] alloc_skb_with_frags+0xc5/0xa60 net/core/skbuff.c:6712 sock_alloc_send_pskb+0xacc/0xc60 net/core/sock.c:2995 tun_alloc_skb drivers/net/tun.c:1461 [inline] tun_get_user+0x1142/0x6c60 drivers/net/tun.c:1794 tun_chr_write_iter+0x3e9/0x5c0 drivers/net/tun.c:1999 new_sync_write fs/read_write.c:593 [inline] vfs_write+0xbe2/0x15d0 fs/read_write.c:686 ksys_write fs/read_write.c:738 [inline] __do_sys_write fs/read_write.c:749 [inline] __se_sys_write fs/read_write.c:746 [inline] __x64_sys_write+0x1fb/0x4d0 fs/read_write.c:746 x64_sys_call+0x30ab/0x3e70 arch/x86/include/generated/asm/syscalls_64.h:2 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xd3/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f

CPU: 0 UID: 0 PID: 6465 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(none) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025

Patch / fix

  • Linux Linux 5.10.249, 5.15.199, 6.1.162, 6.6.122, 6.8, 6.12.67, 6.18.7, 6.19
  • linux Debian 12 6.1.162-1
  • linux Debian 13 6.12.69-1
  • linux Debian 14 6.18.8-1

debian advisories DEBIAN-CVE-2026-23003

  • linux Ubuntu 22.04 LTS 5.15.0-176.186
  • linux Ubuntu 24.04 LTS 6.8.0-117.117
  • linux-aws Ubuntu 22.04 LTS 5.15.0-1105.112
  • linux-aws Ubuntu 24.04 LTS 6.8.0-1055.58
  • linux-gcp Ubuntu 22.04 LTS 5.15.0-1105.114
  • linux-gcp Ubuntu 24.04 LTS 6.8.0-1058.61
  • linux-gke Ubuntu 22.04 LTS 5.15.0-1101.107
  • linux-gke Ubuntu 24.04 LTS 6.8.0-1054.60

ubuntu advisories UBUNTU-CVE-2026-23003

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • kernel RHEL 10.2 6.12.0-211.50.1.el10_2
  • rv RHEL 10.2 6.12.0-211.50.1.el10_2
  • perf RHEL 10.2 6.12.0-211.50.1.el10_2
  • rtla RHEL 10.2 6.12.0-211.50.1.el10_2
  • libperf RHEL 10.2 6.12.0-211.50.1.el10_2
  • kernel-rt RHEL 10.2 6.12.0-211.50.1.el10_2
  • kernel-64k RHEL 10.2 6.12.0-211.50.1.el10_2
  • kernel-core RHEL 10.2 6.12.0-211.50.1.el10_2

red hat advisories RHSA-2026:61887RHSA-2026:59723

  • kernel-64kb SLE Module for Basesystem 15 SP7 6.4.0-150700.53.34.1
  • kernel-syms SLE Module for Development Tools 15 SP7 6.4.0-150700.53.34.1
  • kernel-azure SLE Module for Public Cloud 15 SP7 6.4.0-150700.53.34.1
  • kernel-source SLE Module for Development Tools 15 SP7, SLE Module for Basesystem 15 SP7 6.4.0-150700.53.34.1
  • kernel-default SLE Workstation Extension 15 SP7, SLE Module for Legacy 15 SP7, SLE Module for Basesystem 15 SP7 +2 more 6.4.0-150700.53.34.1
  • kernel-zfcpdump SLE Module for Basesystem 15 SP7 6.4.0-150700.53.34.1
  • kernel-obs-build SLE Module for Development Tools 15 SP7 6.4.0-150700.53.34.1
  • kernel-default-base SLE Module for Basesystem 15 SP7 6.4.0-150700.53.34.1.150700.17.23.1

suse advisories SUSE-SU-2026:4282-1SUSE-SU-2026:1081-1SUSE-SU-2026:1078-1SUSE-SU-2026:20873-1SUSE-SU-2026:20838-1SUSE-SU-2026:20931-1

  • kernel-rt openSUSE Leap 16.0 6.12.0-160000.27.1
  • dtb-aarch64 openSUSE Leap 16.0 6.12.0-160000.27.1
  • kernel-64kb openSUSE Leap 16.0 6.12.0-160000.27.1
  • kernel-syms openSUSE Leap 16.0 6.12.0-160000.27.1
  • kernel-azure openSUSE Leap 16.0 6.12.0-160000.27.1
  • kernel-obs-qa openSUSE Leap 16.0 6.12.0-160000.27.1
  • kernel-source openSUSE Leap 16.0 6.12.0-160000.27.1
  • kernel-default openSUSE Leap 16.0 6.12.0-160000.27.1

opensuse advisories openSUSE-SU-2026:20416-1

  • kernel AlmaLinux 10 6.12.0-211.50.1.el10_2
  • rv AlmaLinux 10 6.12.0-211.50.1.el10_2
  • perf AlmaLinux 10 6.12.0-211.50.1.el10_2
  • rtla AlmaLinux 10 6.12.0-211.50.1.el10_2
  • libperf AlmaLinux 10 6.12.0-211.50.1.el10_2
  • kernel-rt AlmaLinux 10 6.12.0-211.50.1.el10_2
  • kernel-64k AlmaLinux 10 6.12.0-211.50.1.el10_2
  • kernel-core AlmaLinux 10 6.12.0-211.50.1.el10_2

almalinux advisories ALSA-2026:61887ALSA-2026:59723

  • kernel Rocky Linux 10 6.12.0-211.50.1.el10_2
  • kernel Rocky Linux 9 5.14.0-687.42.1.el9_8

rocky linux advisories RLSA-2026:61887RLSA-2026:59723

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-23003 updated cvss 6.1

kernel: ip6_tunnel: use skb_vlan_inet_prepare() in __ip6_tnl_rcv()

  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 9 kernel-rt, kernel-rt-kvm, kernel-rt-core, kernel-rt-modules, kernel-rt-debug-kvm, kernel-rt-debug-core, +12 more
    affected: no fix available
  • Red Hat Enterprise Linux AppStream (v. 9) rv 5.14.0-687.42.1.el9_8, perf 5.14.0-687.42.1.el9_8, rtla 5.14.0-687.42.1.el9_8, python3-perf 5.14.0-687.42.1.el9_8, kernel-devel-matched 5.14.0-687.42.1.el9_8, kernel-64k-devel-matched 5.14.0-687.42.1.el9_8, +7 more
    fixed: vendor fix RHSA-2026:59723
  • Red Hat Enterprise Linux AppStream (v. 10) rv 6.12.0-211.50.1.el10_2, perf 6.12.0-211.50.1.el10_2, rtla 6.12.0-211.50.1.el10_2, python3-perf 6.12.0-211.50.1.el10_2, kernel-devel-matched 6.12.0-211.50.1.el10_2, kernel-64k-devel-matched 6.12.0-211.50.1.el10_2, +7 more
    fixed: vendor fix RHSA-2026:61887
  • Red Hat Enterprise Linux BaseOS (v. 9) kernel 5.14.0-687.42.1.el9_8, kernel-64k 5.14.0-687.42.1.el9_8, kernel-core 5.14.0-687.42.1.el9_8, kernel-tools 5.14.0-687.42.1.el9_8, kernel-modules 5.14.0-687.42.1.el9_8, kernel-64k-core 5.14.0-687.42.1.el9_8, +27 more
    fixed: vendor fix RHSA-2026:59723
  • Red Hat Enterprise Linux BaseOS (v. 10) kernel 6.12.0-211.50.1.el10_2, kernel-64k 6.12.0-211.50.1.el10_2, kernel-core 6.12.0-211.50.1.el10_2, kernel-tools 6.12.0-211.50.1.el10_2, kernel-modules 6.12.0-211.50.1.el10_2, kernel-64k-core 6.12.0-211.50.1.el10_2, +28 more
    fixed: vendor fix RHSA-2026:61887
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) libperf 5.14.0-687.42.1.el9_8, kernel-debuginfo-common-s390x 5.14.0-687.42.1.el9_8, kernel-debuginfo-common-x86_64 5.14.0-687.42.1.el9_8, kernel-debuginfo-common-aarch64 5.14.0-687.42.1.el9_8, kernel-debuginfo-common-ppc64le 5.14.0-687.42.1.el9_8
    fixed: vendor fix RHSA-2026:59723
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) libperf 6.12.0-211.50.1.el10_2, kernel-debuginfo-common-s390x 6.12.0-211.50.1.el10_2, kernel-debuginfo-common-x86_64 6.12.0-211.50.1.el10_2, kernel-debuginfo-common-aarch64 6.12.0-211.50.1.el10_2, kernel-debuginfo-common-ppc64le 6.12.0-211.50.1.el10_2
    fixed: vendor fix RHSA-2026:61887
show 5 more
  • Red Hat Enterprise Linux Real Time (v. 9) kernel-rt 5.14.0-687.42.1.el9_8, kernel-rt-64k 5.14.0-687.42.1.el9_8, kernel-rt-core 5.14.0-687.42.1.el9_8, kernel-rt-modules 5.14.0-687.42.1.el9_8, kernel-rt-64k-core 5.14.0-687.42.1.el9_8, kernel-rt-debug-core 5.14.0-687.42.1.el9_8, +14 more
    fixed: vendor fix RHSA-2026:59723
  • Red Hat Enterprise Linux Real Time (v. 10) kernel-rt 6.12.0-211.50.1.el10_2, kernel-rt-64k 6.12.0-211.50.1.el10_2, kernel-rt-core 6.12.0-211.50.1.el10_2, kernel-rt-modules 6.12.0-211.50.1.el10_2, kernel-rt-64k-core 6.12.0-211.50.1.el10_2, kernel-rt-debug-core 6.12.0-211.50.1.el10_2, +14 more
    fixed: vendor fix RHSA-2026:61887
  • Red Hat Enterprise Linux Real Time for NFV (v. 9) kernel-rt 5.14.0-687.42.1.el9_8, kernel-rt-core 5.14.0-687.42.1.el9_8, kernel-rt-modules 5.14.0-687.42.1.el9_8, kernel-rt-debug-core 5.14.0-687.42.1.el9_8, kernel-rt-modules-core 5.14.0-687.42.1.el9_8, kernel-rt-debug-modules 5.14.0-687.42.1.el9_8, +4 more
    fixed: vendor fix RHSA-2026:59723
  • Red Hat Enterprise Linux Real Time for NFV (v. 10) kernel-rt 6.12.0-211.50.1.el10_2, kernel-rt-core 6.12.0-211.50.1.el10_2, kernel-rt-modules 6.12.0-211.50.1.el10_2, kernel-rt-debug-core 6.12.0-211.50.1.el10_2, kernel-rt-modules-core 6.12.0-211.50.1.el10_2, kernel-rt-debug-modules 6.12.0-211.50.1.el10_2, +4 more
    fixed: vendor fix RHSA-2026:61887
  • Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

cisa ICSA-26-295-11 updated cvss 7.5

Siemens SIMATIC S7-1500 CPU 1518(F)-4 PN/DP MFP

  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) >= 3.1.7 Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) >= 3.1.7 Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) >= 3.1.7 Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0) >= 3.1.7 Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0) >= 3.1.7
    affected: mitigation, no fix available

Facts from CISA's republication of the vendor's own advisory (CSAF); the linked advisory is the authoritative source. CISA notification · csaf

cisa ICSA-26-209-04 updated cvss 7.5

Siemens SIMATIC S7-1500 CPU 1518(F)-4 PN/DP MFP

  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) >= 3.1.6 Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) >= 3.1.6 Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) >= 3.1.6 Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0) >= 3.1.6 Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0) >= 3.1.6
    affected: mitigation, no fix available

Facts from CISA's republication of the vendor's own advisory (CSAF); the linked advisory is the authoritative source. CISA notification · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
4 mo ago

Exploit prediction

0.55% chance of exploitation in the next 30 days, higher than 46% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected products

  • Linux Linux
  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP
  • Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP
  • Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP

Classification

Weakness
  • CWE-457 Use of Uninitialized Variable
  • CWE-908 Use of Uninitialized Resource
Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.