Look up another CVE · open CVE-2026-72320 in the interactive tracker
CVE-2026-72320
netfilter: nft_lookup: fix catchall element handling with inverted lookups
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-2026-72320 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 | 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
nft_lookup_eval() decides whether a lookup matched (`found`) from the direct set lookup and priv->invert before falling back to the catchall element used by interval sets (e.g. nft_set_rbtree) for the open-ended default range. Since `found` is never recomputed after `ext` is replaced by the catchall lookup, inverted lookups (NFT_LOOKUP_F_INV, "!= @set") can wrongly match or wrongly skip the catchall element, producing the wrong verdict. Fold the catchall lookup into `ext` before computing `found`, matching the order already used by nft_objref_map_eval().
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/nft_lookup.c
- What this is
- NETFILTERMAINTAINERS section matched on net/netfilter/ · netfilter-devel@vger.kernel.org · Maintained
- Kernel module
- nf_tables
Check it on the machine
grep -wE 'CONFIG_NETFILTER|CONFIG_NF_TABLES' /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_tablesPrints 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_TABLES
- 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
- 9.1 critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Nsource recompute it - Attack vector
- network (AV:N)source
- EPSS
- 0.52%, higher than 43.1% 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 |
|---|---|---|
| 5.13 | 6.12.97 | 0ab8880865f9 |
| 5.13 | 6.18.40 | 238c612357b5 |
| 5.13 | 7.1.5 | ef0c7d4b04a0 |
| 5.13 | 7.2 | e6107a4c74b5 |
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
- nft_lookup_eval() runs on the netfilter packet datapath via nft_do_chain() for ingress/forward/prerouting hooks, so a remote sender can reach the bug by sending packets evaluated against an affected inverted lookup rule on a catchall interval set.
- AC:LAttack complexity, low
- Once such a ruleset exists, the attacker reliably controls whether the lookup key hits a set element or the catchall by crafting packet fields; no race, memory layout dependency, or other uncontrollable victim state is required.
- PR:NPrivileges required, none
- Exploitation at runtime only requires sending network traffic through the victim's nftables hooks; although rule installation needs CAP_NET_ADMIN, the remote attacker needs no credentials or local privileges on the target system.
- UI:NUser interaction, none
- No victim user interaction is needed beyond normal network traffic processing; the kernel automatically evaluates the inverted lookup expression for each matching packet.
- S:UScope, unchanged
- The impact is incorrect nftables verdicts within the host/kernel network security authority and does not cross VM, container-host, or IOMMU security boundaries.
- C:HConfidentiality impact, high
- Wrongly matching or skipping the catchall element can bypass intended filtering and expose protected internal services or data that the firewall policy was meant to block from the attacker's network position.
- I:HIntegrity impact, high
- The bug can apply or omit catchall set-element actions and verdicts (accept/drop/jump), allowing unauthorized traffic handling contrary to the administrator's intended nftables policy.
- A:NAvailability impact, none
- This is a pure logic error that returns incorrect verdicts without memory corruption, kernel oops/panic, hang, or other direct loss of kernel availability.