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CVE-2026-64410
netfilter: flowtable: IPIP tunnel hardware offload is not yet support
Published 2026-07-25 (3 months ago) by the Linux kernel CNA. Subsystem include/net. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-64410 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 | not affected | 6.1.190-1 | Nothing to do. bookworm never shipped the vulnerable code. |
| Debian 13trixie | not affected | 6.12.113-1 | Nothing to do. trixie never shipped the vulnerable code. |
| Debian 14forky | fixed | 7.1.4-1 | Update the kernel and reboot. Fixed in 7.1.4-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.4-1 | Update the kernel and reboot. Fixed in 7.1.4-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
No driver supports for IPIP tunnels yet, give up early on setting up the hardware offload for this scenario. This patch adds a stub that can be enhanced to add more configuration that are currently not supported. As of now, the offload work is enqueued to the worker, then ignored if the hardware offload configuration is not supported. Check the NF_FLOW_HW flag to know if this entry was already tried once to be offloaded so this is not retried on refresh when unsupported. Move NF_FLOW_HW flag check to nf_flow_offload_add(). If this NF_FLOW_HW flag is unset the _del and _stats variants are never called. This can be updated later on to skip hardware offload work to be queued in case hardware offload does not support it.
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.
include/net/netfilter/nf_flow_table.h
net/netfilter/nf_flow_table_core.c
net/netfilter/nf_flow_table_offload.c
- What this is
- NETFILTERMAINTAINERS section matched on include/net/netfilter/ · netfilter-devel@vger.kernel.org · Maintained
- Kernel module
- nf_flow_table
Check it on the machine
grep -wE 'CONFIG_NETFILTER|CONFIG_NF_FLOW_TABLE' /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_flow_tablePrints 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_FLOW_TABLE
- 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
- 2026-07-25 (3 months ago)source
- CVSS
- 9.8 critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- network (AV:N)source
- EPSS
- 0.55%, higher than 45.0% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- Subsystem
- include/net
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.19 | 7.1.4 | 9efe838c1313 |
| 6.19 | 7.2 | 6c5dcab95f4c |
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:NAttack vector, network
- On a router with an IPIP tunnel and hardware-enabled nftables flowtable, remote TCP or UDP traffic reaches nft_flow_offload_eval and causes the unsupported hardware-offload work. No local syscall access is required from the attacker.
- AC:LAttack complexity, low
- Once the affected deployment is configured, confirmed attacker-controlled flows reliably trigger rule generation and refresh retries without a race or other condition outside the attacker's control.
- PR:NPrivileges required, none
- Creating the tunnel and flowtable requires CAP_NET_ADMIN, but these are deployment prerequisites; an attacker sending traffic through an already configured router needs no privileges or authentication.
- UI:NUser interaction, none
- Packet processing and hardware-rule installation occur automatically without any victim user action.
- S:UScope, unchanged
- The vulnerable netfilter logic and the affected forwarding, driver, and kernel resources remain under the same kernel security authority.
- C:HConfidentiality impact, high
- The generated hardware rules omit the IPIP outer-match and encapsulation semantics, potentially forwarding complete inner-flow contents outside the intended tunnel isolation and onto an unintended network.
- I:HIntegrity impact, high
- A false hardware rule can match spoofed plain inner packets on physical ingress and redirect them as though they were properly decapsulated, bypassing software netfilter and enabling attacker-chosen payload injection.
- A:HAvailability impact, high
- Attackers can create many eligible flows, causing repeated unsupported offload work and consumption of driver or hardware rule resources. Incorrectly accepted rules can also blackhole tunnel traffic, permitting sustained loss of network service.