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CVE-2026-72419
netfilter: nf_nat: avoid invalid nat_net pointer use on failed nf_nat_init()
Published 2026-08-15 (2 months ago) by the Linux kernel CNA. Subsystem net/netfilter. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-72419 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | fixed | 6.1.180-1 | Update the kernel and reboot. Fixed in 6.1.180-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixed | 6.12.100-1 | Update the kernel and reboot. Fixed in 6.12.100-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
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: <TASK> […] 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 </TASK> ================================================================== The out-of-bounds report, though, is a red herring as it is f ---truncated---
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
net/netfilter/nf_nat_core.c
- What this is
- NETFILTERMAINTAINERS section matched on net/netfilter/ · netfilter-devel@vger.kernel.org · Maintained
- Kernel module
- nf_nat
Check it on the machine
grep -wE 'CONFIG_NETFILTER|CONFIG_NF_NAT' /boot/config-$(uname -r)Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.
lsmod | grep -w nf_natPrints a line if that module is loaded right now, and nothing if it is not. One that is not loaded can still be loaded later by anything that needs it.
Show whether Debian builds this, per release
Debian builds this as a loadable module. Every release below compiles it as a module on every flavour, so whether the code is in the running kernel depends on whether that module is loaded.
- bookworm, trixie, forky, sidm
- m
- a loadable module on every flavour - check lsmod, can be blacklisted
- Build switches
- CONFIG_NETFILTER, CONFIG_NF_NAT
- Reads as
- all on means the file is compiled; any one off means it is not.
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages
Signals
- Published
- 2026-08-15 (2 months ago)source
- CVSS
- 7.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.18%, higher than 6.6% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- net/netfilter
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.1 | 6.1.178 | 359d8ff97362 |
| 6.1 | 6.6.145 | 87f7a720de25 |
| 6.1 | 6.12.97 | e794f633021d |
| 6.1 | 6.18.40 | a73e7ac3f3b6 |
| 6.1 | 7.1.5 | eb14aba91163 |
| 6.1 | 7.2 | 069cfe3de2a5 |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:LAttack vector, local
- The bug is reached via the netfilter netlink path (sendmsg on NETLINK_NETFILTER) when creating an nftables NAT chain; nf_tables_newchain -> nf_tables_register_hook -> nf_nat_register_fn. This is a local syscall/configuration interface, not remote packet handling.
- AC:LAttack complexity, low
- Once nf_nat built-in init has failed and another per-net consumer reuses the stale nat_net_id, a CAP_NET_ADMIN caller can deterministically trigger the type confusion by adding/removing a NAT chain; no race, memory-layout gamble, or victim interaction is required.
- PR:LPrivileges required, low
- nfnetlink_rcv requires CAP_NET_ADMIN via netlink_net_capable(); on systems with user namespaces this capability is available to an unprivileged local user (e.g. unshare -Urn), not only init-namespace root.
- UI:NUser interaction, none
- Exploitation is performed entirely by the attacker configuring nftables NAT chains over netlink; no action by another user or administrator is required beyond the attacker’s own netfilter setup.
- S:UScope, unchanged
- Impact is kernel memory corruption and privilege escalation within the same host/kernel security domain; it does not cross a VM, container-to-host, or IOMMU boundary by itself.
- C:HConfidentiality impact, high
- Stale nat_net_id makes net_generic() return a synproxy_net (24 bytes) misinterpreted as nat_net (176 bytes), causing slab out-of-bounds reads; KASAN confirmed an 8-byte OOB read and type confusion can expose adjacent per-net/kernel heap data.
- I:HIntegrity impact, high
- nf_nat_register_fn()/unregister_fn() write nat_hook_ops pointers, user counters, and hook entry tables through the mis-typed smaller structure, corrupting adjacent per-net memory and enabling further arbitrary write/control-flow hijack primitives.
- A:HAvailability impact, high
- The mis-typed per-net access triggers KASAN slab-out-of-bounds faults and can kernel oops/panic during NAT hook registration; corrupted synproxy/per-net state can also crash or hang the system on subsequent netfilter activity.