CVE-2022-48719: net, neigh: Do not trigger immediate probes on NUD_FAILED from neigh_managed_work
In the Linux kernel, the following vulnerability has been resolved:
net, neigh: Do not trigger immediate probes on NUD_FAILED from neigh_managed_work
syzkaller was able to trigger a deadlock for NTF_MANAGED entries [0]:
kworker/0:16/14617 is trying to acquire lock:
ffffffff8d4dd370 (&tbl->lock){++-.}-{2:2}, at: ___neigh_create+0x9e1/0x2990 net/core/neighbour.c:652
[...]
but task is already holding lock:
ffffffff8d4dd370 (&tbl->lock){++-.}-{2:2}, at: neigh_managed_work+0x35/0x250 net/core/neighbour.c:1572
The neighbor entry turned to NUD_FAILED state, where __neigh_event_send()
triggered an immediate probe as per commit cd28ca0a3dd1 ("neigh: reduce
arp latency") via neigh_probe() given table lock was held.
One option to fix this situation is to defer the neigh_probe() back to
the neigh_timer_handler() similarly as pre cd28ca0a3dd1. For the case
of NTF_MANAGED, this deferral is acceptable given this only happens on
actual failure state and regular / expected state is NUD_VALID with the
entry already present.
The fix adds a parameter to __neigh_event_send() in order to communicate
whether immediate probe is allowed or disallowed. Existing call-sites
of neigh_event_send() default as-is to immediate probe. However, the
neigh_managed_work() disables it via use of neigh_event_send_probe().
[0] <TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
print_deadlock_bug kernel/locking/lockdep.c:2956 [inline]
check_deadlock kernel/locking/lockdep.c:2999 [inline]
validate_chain kernel/locking/lockdep.c:3788 [inline]
__lock_acquire.cold+0x149/0x3ab kernel/locking/lockdep.c:5027
lock_acquire kernel/locking/lockdep.c:5639 [inline]
lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5604
__raw_write_lock_bh include/linux/rwlock_api_smp.h:202 [inline]
_raw_write_lock_bh+0x2f/0x40 kernel/locking/spinlock.c:334
___neigh_create+0x9e1/0x2990 net/core/neighbour.c:652
ip6_finish_output2+0x1070/0x14f0 net/ipv6/ip6_output.c:123
__ip6_finish_output net/ipv6/ip6_output.c:191 [inline]
__ip6_finish_output+0x61e/0xe90 net/ipv6/ip6_output.c:170
ip6_finish_output+0x32/0x200 net/ipv6/ip6_output.c:201
NF_HOOK_COND include/linux/netfilter.h:296 [inline]
ip6_output+0x1e4/0x530 net/ipv6/ip6_output.c:224
dst_output include/net/dst.h:451 [inline]
NF_HOOK include/linux/netfilter.h:307 [inline]
ndisc_send_skb+0xa99/0x17f0 net/ipv6/ndisc.c:508
ndisc_send_ns+0x3a9/0x840 net/ipv6/ndisc.c:650
ndisc_solicit+0x2cd/0x4f0 net/ipv6/ndisc.c:742
neigh_probe+0xc2/0x110 net/core/neighbour.c:1040
__neigh_event_send+0x37d/0x1570 net/core/neighbour.c:1201
neigh_event_send include/net/neighbour.h:470 [inline]
neigh_managed_work+0x162/0x250 net/core/neighbour.c:1574
process_one_work+0x9ac/0x1650 kernel/workqueue.c:2307
worker_thread+0x657/0x1110 kernel/workqueue.c:2454
kthread+0x2e9/0x3a0 kernel/kthread.c:377
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
</TASK>
Security readout for executives and security teams
Plain-English summary
CVE-2022-48719 is a Linux kernel networking deadlock. Under specific neighbor-table conditions, the kernel can lock itself while handling a failed managed neighbor entry. The documented impact is availability, not data theft or code execution. Public sources do not show active exploitation.
Executive priority
Treat as a routine-to-priority kernel availability fix. It is not currently supported as an emergency exploitation event, but affected network-critical Linux systems should be patched through normal accelerated maintenance.
Technical view
The flaw is in Linux net/core/neighbour.c. For NTF_MANAGED entries entering NUD_FAILED, __neigh_event_send() could trigger an immediate neigh_probe() while neigh_managed_work() already held the neighbor table lock, causing recursive lock acquisition and deadlock. The fix disables immediate probing from this path and defers probing.
Likely exposure
Exposure is limited to Linux systems running affected kernel builds in the 5.16-era ranges identified by the CVE data. Systems using vendor kernels need vendor mapping because distributions often backport fixes without changing major kernel versions.
Exploitation context
The issue was found by syzkaller. The source describes a deadlock trace, not a public exploit. CISA KEV status is false in the provided data, so there is no cited evidence of active exploitation.
Researcher notes
Evidence is limited to the CVE description and Linux stable commits. No CVSS, CWE, exploitability assessment, or broad affected distribution list is provided. Validate exposure by source commit presence or vendor backport status, not only version string.
Mitigation direction
Apply a Linux kernel update containing the referenced stable fixes.
Check your distribution’s advisory for backported fixes to CVE-2022-48719.
Prioritize internet-facing or network-critical Linux systems if affected.
Validation and detection
Inventory Linux kernel versions across servers, appliances, and containers hosts.
Compare installed kernels with vendor advisories for CVE-2022-48719.
Confirm whether referenced stable commits are present in custom kernels.
Review kernel logs for neighbor-table or lockdep deadlock warnings.
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Potential ATT&CK relevance
Conservative CVE-to-ATT&CK context
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ATT&CK lookup starting points
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CVE-2022-48719 mapping review
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