CVE-2026-23003

Description

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

CVSS Metrics

• v3.1•MEDIUM•Score: 5.5CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
• v3.1•HIGH•Score: 7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS Trends

Current EPSS score: 0.49%• Percentile: 41%

Techniques & Countermeasures

• CWE-908•Use of Uninitialized Resource

  The product uses or accesses a resource that has not been initialized.

Affected Systems

• debian•linux

  < 5.10.249-1 | < 6.1.162-1 | < 6.12.69-1 | < 6.18.8-1

• debian•linux-6.1

  < 6.1.162-1~deb11u1

• ubuntu•linux

  all | < 5.15.0-176.186 | < 6.8.0-117.117 | all

• ubuntu•linux-allwinner-5.19

  all

• ubuntu•linux-aws

  all | < 5.15.0-1105.112 | < 6.8.0-1055.58 | all

• ubuntu•linux-aws-5.0

  all

• ubuntu•linux-aws-5.11

  all

• ubuntu•linux-aws-5.13

  all

• ubuntu•linux-aws-5.15

  < 5.15.0-1105.112~20.04.1

• ubuntu•linux-aws-5.19

  all

• ubuntu•linux-aws-5.3

  all

• ubuntu•linux-aws-5.4

  all

• ubuntu•linux-aws-5.8

  all

• ubuntu•linux-aws-6.14

  all

• ubuntu•linux-aws-6.17

  all

• ubuntu•linux-aws-6.2

  all

• ubuntu•linux-aws-6.5

  all

• ubuntu•linux-aws-6.8

  < 6.8.0-1057.60~22.04.1

• ubuntu•linux-aws-fips

  all | < 5.15.0-1105.112+fips1 | < 6.8.0-1055.58+fips1

• ubuntu•linux-aws-hwe

  all

• ubuntu•linux-azure

  all | all | < 5.15.0-1110.119 | < 6.8.0-1056.62 | all

• ubuntu•linux-azure-4.15

  all

• ubuntu•linux-azure-5.11

  all

• ubuntu•linux-azure-5.13

  all

• ubuntu•linux-azure-5.15

  < 5.15.0-1110.119~20.04.1

• ubuntu•linux-azure-5.19

  all

• ubuntu•linux-azure-5.3

  all

• ubuntu•linux-azure-5.4

  all

• ubuntu•linux-azure-5.8

  all

• ubuntu•linux-azure-6.11

  all

• ubuntu•linux-azure-6.14

  all

• ubuntu•linux-azure-6.17

  < 6.17.0-1021.21~24.04.1

• ubuntu•linux-azure-6.2

  all

• ubuntu•linux-azure-6.5

  all

• ubuntu•linux-azure-6.8

  < 6.8.0-1059.65~22.04.1

• ubuntu•linux-azure-edge

  all

• ubuntu•linux-azure-fde

  all | all | all | all

• ubuntu•linux-azure-fde-5.19

  all

• ubuntu•linux-azure-fde-6.14

  all

• ubuntu•linux-azure-fde-6.2

  all

• ubuntu•linux-azure-fde-6.8

  all

• ubuntu•linux-azure-fips

  all | < 5.15.0-1110.119+fips1 | < 6.8.0-1059.65+fips1

• ubuntu•linux-azure-nvidia

  all

• ubuntu•linux-azure-nvidia-6.14

  all

• ubuntu•linux-bluefield

  all | all | < 5.15.0-1089.91 | < 6.8.0-1022.26

• ubuntu•linux-fips

  all | < 5.15.0-176.186+fips1 | < 6.8.0-116.116+fips1

• ubuntu•linux-gcp

  all | all | < 5.15.0-1105.114 | < 6.8.0-1058.61 | all

• ubuntu•linux-gcp-4.15

  all

• ubuntu•linux-gcp-5.11

  all

• ubuntu•linux-gcp-5.13

  all

Showing first 50 affected entries in server-rendered view.

References (40)

• https://git.kernel.org/stable/c/2f03dafea0a8096a2eb60f551218b360e5bab9a3
• https://git.kernel.org/stable/c/df5ffde9669314500809bc498ae73d6d3d9519ac
• https://git.kernel.org/stable/c/b9f915340f25cae1562f18e1eb52deafca328414
• https://git.kernel.org/stable/c/81c734dae203757fb3c9eee6f9896386940776bd
• https://git.kernel.org/stable/c/f9c5c5b791d3850570796f9e067629474e613796
• https://git.kernel.org/stable/c/64c71d60a21a9ed0a802483dcd422b5b24eb1abe
• https://git.kernel.org/stable/c/9e1c8c2a33d0a7b1f637b5d0602fe56ed10166af
• https://cert-portal.siemens.com/productcert/html/ssa-019113.html
• https://ubuntu.com/security/CVE-2026-23003
• https://www.cve.org/CVERecord?id=CVE-2026-23003
• https://git.kernel.org/linus/81c734dae203757fb3c9eee6f9896386940776bd
• https://ubuntu.com/security/notices/USN-8162-1
• https://ubuntu.com/security/notices/USN-8180-1
• https://ubuntu.com/security/notices/USN-8180-2
• https://ubuntu.com/security/notices/USN-8186-1
• https://ubuntu.com/security/notices/USN-8187-1
• https://ubuntu.com/security/notices/USN-8188-1
• https://ubuntu.com/security/notices/USN-8180-3
• https://ubuntu.com/security/notices/USN-8180-4
• https://ubuntu.com/security/notices/USN-8180-5
• https://ubuntu.com/security/notices/USN-8243-1
• https://ubuntu.com/security/notices/USN-8180-6
• https://ubuntu.com/security/notices/USN-8275-1
• https://ubuntu.com/security/notices/USN-8278-1
• https://ubuntu.com/security/notices/USN-8289-1
• https://ubuntu.com/security/notices/USN-8296-1
• https://ubuntu.com/security/notices/USN-8297-1
• https://ubuntu.com/security/notices/USN-8296-2
• https://ubuntu.com/security/notices/USN-8289-2
• https://ubuntu.com/security/notices/USN-8278-2
• https://ubuntu.com/security/notices/USN-8393-1
• https://ubuntu.com/security/notices/USN-8440-1
• https://ubuntu.com/security/notices/USN-8499-1
• https://ubuntu.com/security/notices/USN-8570-1
• https://ubuntu.com/security/notices/USN-8594-1
• https://ubuntu.com/security/notices/USN-8604-1
• https://ubuntu.com/security/notices/USN-8605-1
• https://ubuntu.com/security/notices/USN-8570-2
• https://security-tracker.debian.org/tracker/CVE-2026-23003
• https://ubuntu.com/security/notices/USN-8669-1