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CVE-2026-63858
netfilter: nf_tables: add hook transactions for device deletions
Published 2026-07-19 (3 months ago) by the Linux kernel CNA. Subsystem include/net. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-63858 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
Restore the flag that indicates that the hook is going away, ie. NFT_HOOK_REMOVE, but add a new transaction object to track deletion of hooks without altering the basechain/flowtable hook_list during the preparation phase. The existing approach that moves the hook from the basechain/flowtable hook_list to transaction hook_list breaks netlink dump path readers of this RCU-protected list. It should be possible use an array for nft_trans_hook to store the deleted hooks to compact the representation but I am not expecting many hook object, specially now that wildcard support for devices is in place. Note that the nft_trans_chain_hooks() list contains a list of struct nft_trans_hook objects for DELCHAIN and DELFLOWTABLE commands, while this list stores struct nft_hook objects for NEWCHAIN and NEWFLOWTABLE. Note that new commands can be updated to use nft_trans_hook for consistency. This patch also adapts the event notification path to deal with the list of hook transactions.
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_tables.h
net/netfilter/nf_tables_api.c
- What this is
- NETFILTERMAINTAINERS section matched on include/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
- 2026-07-19 (3 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
- 0.12%, higher than 2.0% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- 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 |
|---|---|---|
| 5.19 | 6.18.57 | 768daa9f4276 |
| 5.19 | 7.0.10 | 4e69bfb32b2d |
| 5.19 | 7.1 | 10f79dbd7719 |
| 5.10.122 | 0 | 0 |
| 5.15.47 | 0 | 0 |
| 5.17.15 | 0 | 0 |
| 5.18.4 | 0 | 0 |
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 vulnerability is reachable only through local Netlink syscalls to the nf_tables subsystem (NFT_MSG_DELCHAIN/DELFLOWTABLE hook deletion racing with GETCHAIN/GETFLOWTABLE dumps), which per kernel CNA guidance is Attack Vector Local, not network-reachable.
- AC:LAttack complexity, low
- The attacker controls both sides of the race by opening concurrent Netlink sockets—one issuing hook-deletion batch commands and another issuing chain/flowtable dumps—making successful triggering reliably achievable without conditions outside attacker control.
- PR:LPrivileges required, low
- All nf_tables Netlink operations require CAP_NET_ADMIN checked in nfnetlink_rcv(), which is obtainable by an unprivileged user via user namespaces (unshare -Urn), so privileges required are Low rather than High.
- UI:NUser interaction, none
- Exploitation requires no victim interaction; the attacker triggers the race entirely through their own concurrent Netlink requests without needing another user to perform any action.
- S:UScope, unchanged
- Impact remains within the kernel's security authority (kernel crash, memory corruption, potential local privilege escalation) rather than crossing a distinct security boundary such as VM guest-to-host escape.
- C:HConfidentiality impact, high
- RCU list corruption yields a bogus nft_hook pointer that dereferences arbitrary kernel memory (e.g., reading hook->ifname from stack-local or freed memory), constituting arbitrary kernel memory read potential consistent with High confidentiality impact.
- I:HIntegrity impact, high
- The corrupted list traversal produces invalid struct nft_hook pointers via container_of(), enabling heap/stack memory corruption that can be leveraged for arbitrary write or control-flow hijacking, warranting High integrity impact.
- A:HAvailability impact, high
- The race reliably causes kernel oops/panic from dereferencing bogus nft_hook pointers during concurrent Netlink dumps, and the underlying RCU list corruption can crash or hang the system, giving High availability impact.