--- id: CVE-2026-23003 title: 'ip6_tunnel: use skb_vlan_inet_prepare() in __ip6_tnl_rcv()' 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(… severity: high cvss: 7.5 cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H' cvssSource: cna vendor: Linux product: Linux affected: - >- Linux >= a9bc32879a08f23cdb80a48c738017e39aea1080 < f9c5c5b791d3850570796f9e067629474e613796 - >- Linux >= af6b5c50d47ab43e5272ad61935d0ed2e264d3f0 < 64c71d60a21a9ed0a802483dcd422b5b24eb1abe - >- Linux >= d54e4da98bbfa8c257bdca94c49652d81d18a4d8 < 9e1c8c2a33d0a7b1f637b5d0602fe56ed10166af - >- Linux >= 350a6640fac4b53564ec20aa3f4a0922cb0ba5e6 < 2f03dafea0a8096a2eb60f551218b360e5bab9a3 - >- Linux >= 8d975c15c0cd744000ca386247432d57b21f9df0 < df5ffde9669314500809bc498ae73d6d3d9519ac - >- Linux >= 8d975c15c0cd744000ca386247432d57b21f9df0 < b9f915340f25cae1562f18e1eb52deafca328414 - >- Linux >= 8d975c15c0cd744000ca386247432d57b21f9df0 < 81c734dae203757fb3c9eee6f9896386940776bd - Linux c835df3bcc14858ae9b27315dd7de76370b94f3a - Linux >= 5.10.210 < 5.10.249 - Linux >= 5.15.149 < 5.15.199 - Linux >= 6.1.77 < 6.1.162 - Linux >= 6.6.16 < 6.6.122 - Linux >= 6.7.4 < 6.8 - Linux 6.8 ssvc: exploitation: none automatable: 'yes' technicalImpact: partial timestamp: '2026-06-16T20:17:50.477974Z' exploitAvailable: true published: '2026-01-25' updated: '2026-09-08' sourceUpdated: '2026-09-08T08:44:33.646Z' source: CVEORG sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-23003' references: - url: 'https://git.kernel.org/stable/c/f9c5c5b791d3850570796f9e067629474e613796' - url: 'https://git.kernel.org/stable/c/64c71d60a21a9ed0a802483dcd422b5b24eb1abe' - url: 'https://git.kernel.org/stable/c/9e1c8c2a33d0a7b1f637b5d0602fe56ed10166af' - url: 'https://git.kernel.org/stable/c/2f03dafea0a8096a2eb60f551218b360e5bab9a3' - url: 'https://git.kernel.org/stable/c/df5ffde9669314500809bc498ae73d6d3d9519ac' - url: 'https://git.kernel.org/stable/c/b9f915340f25cae1562f18e1eb52deafca328414' - url: 'https://git.kernel.org/stable/c/81c734dae203757fb3c9eee6f9896386940776bd' tags: - cve.org - exploit-available epss: 0.0052 epssPercentile: 0.41742 exploits: github: 1 githubRepos: - >- https://github.com/George0Papasotiriou/CVE-2026-23003-Cross-Chain-Bridge-Message-Forging-via-Missing-Origin-Chain-ID checkedAt: '2026-09-26T09:05:40.316Z' ingestedAt: '2026-09-08T15:33:26.994Z' --- ## Overview 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 ## Affected - `Linux >= a9bc32879a08f23cdb80a48c738017e39aea1080 < f9c5c5b791d3850570796f9e067629474e613796` - `Linux >= af6b5c50d47ab43e5272ad61935d0ed2e264d3f0 < 64c71d60a21a9ed0a802483dcd422b5b24eb1abe` - `Linux >= d54e4da98bbfa8c257bdca94c49652d81d18a4d8 < 9e1c8c2a33d0a7b1f637b5d0602fe56ed10166af` - `Linux >= 350a6640fac4b53564ec20aa3f4a0922cb0ba5e6 < 2f03dafea0a8096a2eb60f551218b360e5bab9a3` - `Linux >= 8d975c15c0cd744000ca386247432d57b21f9df0 < df5ffde9669314500809bc498ae73d6d3d9519ac` - `Linux >= 8d975c15c0cd744000ca386247432d57b21f9df0 < b9f915340f25cae1562f18e1eb52deafca328414` - `Linux >= 8d975c15c0cd744000ca386247432d57b21f9df0 < 81c734dae203757fb3c9eee6f9896386940776bd` - `Linux c835df3bcc14858ae9b27315dd7de76370b94f3a` - `Linux >= 5.10.210 < 5.10.249` - `Linux >= 5.15.149 < 5.15.199` - `Linux >= 6.1.77 < 6.1.162` - `Linux >= 6.6.16 < 6.6.122` - `Linux >= 6.7.4 < 6.8` - `Linux 6.8` ## Remediation Refer to the linked advisories for vendor-supplied fixes and affected version ranges.