CVE-2026-72419
Summary
by MITRE • 08/15/2026
In the Linux kernel, the following vulnerability has been resolved:
netfilter: nf_nat: avoid invalid nat_net pointer use on failed nf_nat_init()
We ran into below KASAN splat, which is mostly uninteresting, beside for having nf_nat_register_fn() in the call chain as a cause for the offending access:
================================================================== BUG: KASAN: slab-out-of-bounds in nf_nat_register_fn+0x5f9/0x640 Read of size 8 at addr ffff890031e54c20 by task iptables/9510
CPU: 0 UID: 0 PID: 9510 Comm: iptables Not tainted 6.18.18-grsec-full-20260320181326 #1 PREEMPT(voluntary) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 Call Trace: […] dump_stack_lvl+0xee/0x160 ffff88004117eeb8
[…] print_report+0x6e/0x640 ffff88004117eee0
[…] ? __phys_addr+0x8e/0x140 ffff88004117eef0
[…] ? kasan_addr_to_slab+0x51/0xe0 ffff88004117ef08
[…] ? complete_report_info+0xec/0x1c0 ffff88004117ef20
[…] ? nf_nat_register_fn+0x5f9/0x640 ffff88004117ef48
[…] kasan_report+0xbc/0x140 ffff88004117ef50
[…] ? nf_nat_register_fn+0x5f9/0x640 ffff88004117ef90
[…] nf_nat_register_fn+0x5f9/0x640 ffff88004117eff8
[…] ? nf_nat_icmp_reply_translation+0x6e0/0x6e0 ffff88004117f070
[…] nf_tables_register_hook.part.0+0xa0/0x220 ffff88004117f080
[…] nf_tables_addchain.constprop.0+0x1054/0x1fc0 ffff88004117f0b8
[…] ? nft_chain_lookup.part.0+0x4ce/0xac0 ffff88004117f130
[…] ? nf_tables_abort+0x3d80/0x3d80 ffff88004117f190
[…] ? nf_tables_dumpreset_obj+0x100/0x100 ffff88004117f1c8
[…] ? nft_table_lookup.part.0+0x255/0x300 ffff88004117f310
[…] ? nf_tables_newchain+0x21a4/0x2fa0 ffff88004117f358
[…] nf_tables_newchain+0x21a4/0x2fa0 ffff88004117f360
[…] ? nf_tables_addchain.constprop.0+0x1fc0/0x1fc0 ffff88004117f458
[…] ? nla_get_range_signed+0x4a0/0x4a0 ffff88004117f488
[…] ? lock_acquire+0x16f/0x320 ffff88004117f490
[…] ? find_held_lock+0x3b/0xe0 ffff88004117f4b0
[…] ? __nla_parse+0x45/0x80 ffff88004117f500
[…] nfnetlink_rcv_batch+0xbca/0x19a0 ffff88004117f550
[…] ? nfnetlink_net_exit_batch+0x120/0x120 ffff88004117f618
[…] ? __sanitizer_cov_trace_switch+0x63/0xe0 ffff88004117f720
[…] ? gr_acl_handle_mmap+0x1c4/0x320 ffff88004117f7c0
[…] ? nla_get_range_signed+0x4a0/0x4a0 ffff88004117f7e8
[…] ? gr_is_capable+0x6f/0xe0 ffff88004117f830
[…] ? __nla_parse+0x45/0x80 ffff88004117f860
[…] ? skb_pull+0x103/0x1a0 ffff88004117f880
[…] nfnetlink_rcv+0x3db/0x4a0 ffff88004117f8b0
[…] ? nfnetlink_rcv_batch+0x19a0/0x19a0 ffff88004117f8d8
[…] ? netlink_lookup+0xe2/0x240 ffff88004117f900
[…] netlink_unicast+0x74b/0xb00 ffff88004117f930
[…] ? netlink_attachskb+0xb20/0xb20 ffff88004117f980
[…] ? __check_object_size+0x3e/0xaa0 ffff88004117f998
[…] ? security_netlink_send+0x51/0x160 ffff88004117f9c8
[…] netlink_sendmsg+0xa03/0x1200 ffff88004117f9f8
[…] ? netlink_unicast+0xb00/0xb00 ffff88004117fa70
[…] ? netlink_unicast+0xb00/0xb00 ffff88004117fac8
[…] ? ____sys_sendmsg+0xe2a/0x1040 ffff88004117faf8
[…] ____sys_sendmsg+0xe2a/0x1040 ffff88004117fb00
[…] ? kernel_recvmsg+0x300/0x300 ffff88004117fb60
[…] ? reacquire_held_locks+0xe9/0x260 ffff88004117fbc8
[…] ___sys_sendmsg+0x138/0x200 ffff88004117fbf8
[…] ? do_recvmmsg+0x7e0/0x7e0 ffff88004117fc30
[…] ? lockdep_hardirqs_on_prepare+0x101/0x1e0 ffff88004117fc50
[…] ? lock_acquire+0x16f/0x320 ffff88004117fd20
[…] ? lock_acquire+0x16f/0x320 ffff88004117fd58
[…] ? find_held_lock+0x3b/0xe0 ffff88004117fd70
[…] __sys_sendmsg+0x17a/0x260 ffff88004117fdc8
[…] ? __sys_sendmsg_sock+0x80/0x80 ffff88004117fdf0
[…] ? syscall_trace_enter+0x15e/0x2c0 ffff88004117fe98
[…] do_syscall_64+0x7d/0x400 ffff88004117fec8
[…] entry_SYSCALL_64_safe_stack+0x4a/0x60 ffff88004117fef8
==================================================================
The out-of-bounds report, though, is a red herring as it is f ---truncated---
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Analysis
by VulDB Data Team • 08/15/2026
The vulnerability in question relates to improper handling of network address translation (NAT) initialization within the Linux kernel's netfilter subsystem. Specifically, when nf_nat_init() fails during the setup of NAT functionality, the code path continues to use a pointer to nat_net that may not have been properly initialized or allocated. This leads to an invalid memory access pattern where nf_nat_register_fn attempts to dereference this dangling pointer, triggering a kernel memory safety violation reported by KASAN as a slab-out-of-bounds error.
The technical flaw manifests in the control flow of NAT module initialization, where error handling does not adequately prevent subsequent use of partially initialized or unset data structures. The call trace shows that the failure originates from iptables attempting to register a NAT hook through nf_tables_register_hook, which eventually calls nf_nat_register_fn, leading to memory access beyond valid bounds. This type of vulnerability falls under CWE-476, representing a Null Pointer Dereference, and can be categorized under ATT&CK technique T1059.003 for execution via system commands like iptables.
The operational impact of this vulnerability could allow an attacker with local access or control over network traffic to potentially cause a kernel panic or execute arbitrary code within the kernel context. Although the KASAN report initially appears to indicate a memory corruption issue, the root cause is in the failure to properly manage state transitions during NAT initialization. The vulnerability is particularly concerning because it involves core netfilter infrastructure that manages packet filtering and NAT operations essential for network security policies.
Mitigation strategies should focus on ensuring robust error handling within the NAT initialization sequence. The fix requires that nf_nat_init() properly checks for allocation failures and ensures that nat_net pointer remains valid before any registration functions attempt to access it. Additionally, developers should implement defensive programming practices such as null-checking pointers before dereferencing them in kernel space, especially in critical initialization paths. System administrators should ensure they are running patched kernel versions where this vulnerability has been addressed through proper state management during NAT module setup and error recovery procedures that prevent invalid pointer usage after failed initialization attempts. The solution aligns with security best practices for kernel development and adherence to secure coding standards outlined in guidelines such as those from the Open Web Application Security Project (OWASP) and CERT Secure Coding standards.