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CVE-2026-53000
netfilter: nat: use kfree_rcu to release ops
Published 2026-06-24 (4 months ago) by the Linux kernel CNA. Subsystem net/ipv4. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-53000 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 | vulnerable | 6.1.190-1 | No fix published anywhere yet, neither in Debian nor upstream for the series bookworm tracks. Watch the Debian tracker page for this CVE. Advisories for bookworm have historically landed a median of 23 days after publication. |
| Debian 13trixie | vulnerable | 6.12.113-1 | No fix published anywhere yet, neither in Debian nor upstream for the series trixie tracks. Watch the Debian tracker page for this CVE. Advisories for trixie have historically landed a median of 11 days after publication. |
| Debian 14forky | fixed | 7.0.10-1 | Update the kernel and reboot. Fixed in 7.0.10-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.0.10-1 | Update the kernel and reboot. Fixed in 7.0.10-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
Florian Westphal says: "Historically this is not an issue, even for normal base hooks: the data path doesn't use the original nf_hook_ops that are used to register the callbacks. However, in v5.14 I added the ability to dump the active netfilter hooks from userspace. This code will peek back into the nf_hook_ops that are available at the tail of the pointer-array blob used by the datapath. The nat hooks are special, because they are called indirectly from the central nat dispatcher hook. They are currently invisible to the nfnl hook dump subsystem though. But once that changes the nat ops structures have to be deferred too." Update nf_nat_register_fn() to deal with partial exposition of the hooks from error path which can be also an issue for nfnetlink_hook.
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/ipv4/netfilter/iptable_nat.c
net/ipv6/netfilter/ip6table_nat.c
net/netfilter/nf_nat_core.c
- What this is
- NETFILTERMAINTAINERS section matched on net/*/netfilter/ · netfilter-devel@vger.kernel.org · Maintained
- Kernel module
- iptable_nat
Check it on the machine
grep -wE 'CONFIG_INET|CONFIG_IP_NF_NAT|CONFIG_NETFILTER' /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 iptable_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, but not on every flavour. At least one release below builds the code on some of its kernel flavours and not on others, so the answer depends on the architecture and flavour installed.
- bookworm, trixiem
- forky, sidMnot built on amd64/rt-amd64, arm64/rt-arm64
- m
- a loadable module on every flavour - check lsmod, can be blacklisted
- M
- a module where it is built at all; some flavours do not build it
- Build switches
- CONFIG_INET, CONFIG_IP_NF_NAT, CONFIG_NETFILTER
- 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
- 2026-06-24 (4 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
- 0.14%, higher than 2.9% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- net/ipv4
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 5.14 | 6.18.33 | 32fdd2e38e74 |
| 5.14 | 7.0.10 | 3c7511f38ab5 |
| 5.14 | 7.1 | 6eda0d771f94 |
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 vulnerable path is reached through local netfilter/nfnetlink operations, including hook dumps and NAT hook registration/unregistration via netlink or xtables control paths. Remote packets may traverse NAT hooks, but the unsafe freed nf_hook_ops metadata is exposed through local control-plane operations.
- AC:LAttack complexity, low
- The relevant race is between hook dumping and NAT hook teardown/error unwind, and an attacker with netfilter control can drive both sides concurrently. There are no required conditions outside the attacker’s influence beyond normal scheduling.
- PR:LPrivileges required, low
- The paths require CAP_NET_ADMIN in the target network namespace. Netfilter/nftables operations are reachable by an unprivileged local user through user and network namespaces, so this is Low rather than High.
- UI:NUser interaction, none
- No victim action is required after the attacker has local execution. The attacker can issue the netlink/xtables operations directly.
- S:UScope, unchanged
- The impact is within the same kernel security authority and represents a standard local kernel memory-safety issue. It does not cross a VM, IOMMU, or similar separate security boundary.
- C:HConfidentiality impact, high
- This is a use-after-free of kernel heap objects referenced by RCU-visible hook metadata. Reclaiming the freed object can drive kernel reads through attacker-influenced nf_hook_ops fields, making high confidentiality impact defensible.
- I:HIntegrity impact, high
- A kernel use-after-free is a memory corruption primitive and may be leveraged beyond a crash with heap grooming. Following the higher-severity rule for UAFs, arbitrary modification or code execution is defensible.
- A:HAvailability impact, high
- The stale hook metadata can be dereferenced after free in kernel context. At minimum this can cause an oops/panic, so availability impact is High.