CVE-2026-23003 [High] | Security Vulnerability in Linux Kernel

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

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-01-26	—	0.02%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-01-26

—

0.02%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
7.5	3.1	HIGH	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H` Click to expand Attack vector (AV:N) Could be attacked over the internet or any normal routed network—not just someone sitting at the machine. Attack complexity (AC:L) Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup. Privileges required (PR:N) No account or special rights needed—anonymous or random user is enough. User interaction (UI:N) Nobody has to click “OK” or open a trap file; it can work without a victim helping. Scope (S:U) Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems. Confidentiality (C:N) Doesn’t really leak secrets in a meaningful way. Integrity (I:N) Data isn’t meaningfully altered or forged. Availability (A:H) Could take the service down hard or make it unusable for people who depend on it.	3.9	3.6	416baaa9-dc9f-4396-8d5f-8c081fb06d67
5.5	3.1	MEDIUM	`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H` Click to expand Attack vector (AV:L) They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by. Attack complexity (AC:L) Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup. Privileges required (PR:L) A normal user session is enough; they don’t have to be admin. User interaction (UI:N) Nobody has to click “OK” or open a trap file; it can work without a victim helping. Scope (S:U) Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems. Confidentiality (C:N) Doesn’t really leak secrets in a meaningful way. Integrity (I:N) Data isn’t meaningfully altered or forged. Availability (A:H) Could take the service down hard or make it unusable for people who depend on it.	1.8	3.6	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

7.5

3.1

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand

Attack vector (AV:N): Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L): Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N): No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N): Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U): Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N): Doesn’t really leak secrets in a meaningful way.
Integrity (I:N): Data isn’t meaningfully altered or forged.
Availability (A:H): Could take the service down hard or make it unusable for people who depend on it.

3.9

3.6

416baaa9-dc9f-4396-8d5f-8c081fb06d67

5.5

3.1

MEDIUM

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H Click to expand

Attack vector (AV:L): They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L): Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L): A normal user session is enough; they don’t have to be admin.
User interaction (UI:N): Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U): Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N): Doesn’t really leak secrets in a meaningful way.
Integrity (I:N): Data isn’t meaningfully altered or forged.
Availability (A:H): Could take the service down hard or make it unusable for people who depend on it.

1.8

3.6

[email protected]

OS Trackers for CVE-2026-23003

vendor	priority	summary	link
`debian`	not yet assigned	CVE-2026-23003 not yet assigned priority: Debian including 2 source packages (linux, linux-6.1), 6 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 6.	https://security-tracker.debian.org/tracker/CVE-2026-23003
`redhat`	medium	—	https://access.redhat.com/security/cve/CVE-2026-23003
`suse`	medium	CVE-2026-23003 severity moderate: SUSE including 419 source package names (2.1.3-6.124:kernel-default-base-6.4.0-40.1.21.17, 2.1.3-7.105:kernel-default-6.4.0-40.1, …), 679 product×package rows across 53 product lines (Container suse/sl-micro/6.0/base-os-container, Container suse/sl-micro/6.0/kvm-os-container, … (53 product lines)): Fixed 341, Known Affected 231, Known Not Affected 82, First Fixed 25.	https://www.suse.com/security/cve/CVE-2026-23003/
`ubuntu`	medium	CVE-2026-23003 medium priority: Ubuntu including 157 source packages (linux, linux-allwinner-5.19, …), 1256 status rows across 8 suites (bionic, focal, jammy, noble, questing, trusty, upstream, xenial): DNE 871, ignored 170, released 102, needed 89, pending 16, not-affected 8.	https://ubuntu.com/security/CVE-2026-23003

Affected software / configurations for CVE-2026-23003

Vendor	Product	Version	Raw CPE
linux	linux_kernel	>= 5.10.210, < 5.10.249	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 5.15.149, < 5.15.199	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 6.1.77, < 6.1.162	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 6.6.16, < 6.6.122	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 6.7.4, < 6.8	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 6.8.1, < 6.12.67	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 6.13, < 6.18.7	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	6.8	cpe:2.3:o:linux:linux_kernel:6.8:-::::::
linux	linux_kernel	6.19	cpe:2.3:o:linux:linux_kernel:6.19:rc1::::::
linux	linux_kernel	6.19	cpe:2.3:o:linux:linux_kernel:6.19:rc2::::::
linux	linux_kernel	6.19	cpe:2.3:o:linux:linux_kernel:6.19:rc3::::::
linux	linux_kernel	6.19	cpe:2.3:o:linux:linux_kernel:6.19:rc4::::::
linux	linux_kernel	6.19	cpe:2.3:o:linux:linux_kernel:6.19:rc5::::::
linux	linux_kernel	6.19	cpe:2.3:o:linux:linux_kernel:6.19:rc6::::::
linux	linux_kernel	6.19	cpe:2.3:o:linux:linux_kernel:6.19:rc7::::::
linux	linux_kernel	6.19	cpe:2.3:o:linux:linux_kernel:6.19:rc8::::::

References for CVE-2026-23003

URL	Tags
https://git.kernel.org/stable/c/2f03dafea0a8096a2eb60f551218b360e5bab9a3	Patch
https://git.kernel.org/stable/c/64c71d60a21a9ed0a802483dcd422b5b24eb1abe	Patch
https://git.kernel.org/stable/c/81c734dae203757fb3c9eee6f9896386940776bd	Patch
https://git.kernel.org/stable/c/9e1c8c2a33d0a7b1f637b5d0602fe56ed10166af	Patch
https://git.kernel.org/stable/c/b9f915340f25cae1562f18e1eb52deafca328414	Patch
https://git.kernel.org/stable/c/df5ffde9669314500809bc498ae73d6d3d9519ac	Patch
https://git.kernel.org/stable/c/f9c5c5b791d3850570796f9e067629474e613796	Patch

URL

CVE-2026-23003 | ip6_tunnel: use skb_vlan_inet_prepare() in __ip6_tnl_rcv()

Exploit prediction scoring system (EPSS) score for CVE-2026-23003

Common vulnerability scoring system (CVSS) metrics for CVE-2026-23003

Weakness enumeration for CVE-2026-23003

OS Trackers for CVE-2026-23003

Affected software / configurations for CVE-2026-23003

References for CVE-2026-23003