Vulnerabilities
- CVSS
- 5.5 Medium
- Vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H- EPSS
- 0.12%
- Risk score
- 1.2
- Published
- 2026-04-13
- Status
- Published
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.
A flaw was found in the Linux kernel's netfilter subsystem, specifically within the x_tables and arptables components. This vulnerability arises when xt_match and xt_target extensions, registered for unspecified protocol families, are incorrectly processed by the Address Resolution Protocol (ARP) subsystem. An attacker could exploit this by crafting network packets that trigger a mismatch in hook validation, leading to a null pointer dereference and ultimately a kernel panic, resulting in a Denial of Service (DoS) for the affected system.
Coverage 6
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