In the Linux kernel, the following vulnerability has been resolved:
netfilter: ipset: fix refcount race between list:set GC and swap
__ip_set_put_byindex() resolved the index to a set pointer under RCU,
then took ip_set_ref_lock in __ip_set_put() to decrement set->ref.
ip_set_swap() holds that same lock while swapping both the ip_set_list
slots and the two sets' ref counters, so it can interleave between the
dereference and the lock acquisition, leaving the caller to decrement a
set whose reference already moved to the other index and hit
BUG_ON(set->ref == 0). list_set_gc() reaches this from timer softirq,
which the nfnl mutex does not serialize against swap: an expiring
list:set member calls list_set_del() -> ip_set_put_byindex() while
IPSET_CMD_SWAP runs on the referenced sets.
Resolve the index and decrement under ip_set_ref_lock, as ip_set_swap()
already does, keeping the refcount tied to the index rather than to a
stale set pointer.
kernel BUG at net/netfilter/ipset/ip_set_core.c:685!
Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI
RIP: 0010:ip_set_put_byindex (net/netfilter/ipset/ip_set_core.c:870)
Call Trace:
<IRQ>
list_set_del (net/netfilter/ipset/ip_set_list_set.c:159)
set_cleanup_entries (net/netfilter/ipset/ip_set_list_set.c:181)
list_set_gc (net/netfilter/ipset/ip_set_list_set.c:578)
call_timer_fn (kernel/time/timer.c:1748)
__run_timers (kernel/time/timer.c:1799 kernel/time/timer.c:2374)
run_timer_softirq (kernel/time/timer.c:2405)
</IRQ>
Kernel panic - not syncing: Fatal exception in interrupt
netfilter: ipset: fix refcount race between list:set GC and swap
__ip_set_put_byindex() resolved the index to a set pointer under RCU,
then took ip_set_ref_lock in __ip_set_put() to decrement set->ref.
ip_set_swap() holds that same lock while swapping both the ip_set_list
slots and the two sets' ref counters, so it can interleave between the
dereference and the lock acquisition, leaving the caller to decrement a
set whose reference already moved to the other index and hit
BUG_ON(set->ref == 0). list_set_gc() reaches this from timer softirq,
which the nfnl mutex does not serialize against swap: an expiring
list:set member calls list_set_del() -> ip_set_put_byindex() while
IPSET_CMD_SWAP runs on the referenced sets.
Resolve the index and decrement under ip_set_ref_lock, as ip_set_swap()
already does, keeping the refcount tied to the index rather than to a
stale set pointer.
kernel BUG at net/netfilter/ipset/ip_set_core.c:685!
Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI
RIP: 0010:ip_set_put_byindex (net/netfilter/ipset/ip_set_core.c:870)
Call Trace:
<IRQ>
list_set_del (net/netfilter/ipset/ip_set_list_set.c:159)
set_cleanup_entries (net/netfilter/ipset/ip_set_list_set.c:181)
list_set_gc (net/netfilter/ipset/ip_set_list_set.c:578)
call_timer_fn (kernel/time/timer.c:1748)
__run_timers (kernel/time/timer.c:1799 kernel/time/timer.c:2374)
run_timer_softirq (kernel/time/timer.c:2405)
</IRQ>
Kernel panic - not syncing: Fatal exception in interrupt
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Fixes
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Workaround
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References
History
Wed, 26 Aug 2026 17:15:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Weaknesses | CWE-362 |
Wed, 26 Aug 2026 14:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: netfilter: ipset: fix refcount race between list:set GC and swap __ip_set_put_byindex() resolved the index to a set pointer under RCU, then took ip_set_ref_lock in __ip_set_put() to decrement set->ref. ip_set_swap() holds that same lock while swapping both the ip_set_list slots and the two sets' ref counters, so it can interleave between the dereference and the lock acquisition, leaving the caller to decrement a set whose reference already moved to the other index and hit BUG_ON(set->ref == 0). list_set_gc() reaches this from timer softirq, which the nfnl mutex does not serialize against swap: an expiring list:set member calls list_set_del() -> ip_set_put_byindex() while IPSET_CMD_SWAP runs on the referenced sets. Resolve the index and decrement under ip_set_ref_lock, as ip_set_swap() already does, keeping the refcount tied to the index rather than to a stale set pointer. kernel BUG at net/netfilter/ipset/ip_set_core.c:685! Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI RIP: 0010:ip_set_put_byindex (net/netfilter/ipset/ip_set_core.c:870) Call Trace: <IRQ> list_set_del (net/netfilter/ipset/ip_set_list_set.c:159) set_cleanup_entries (net/netfilter/ipset/ip_set_list_set.c:181) list_set_gc (net/netfilter/ipset/ip_set_list_set.c:578) call_timer_fn (kernel/time/timer.c:1748) __run_timers (kernel/time/timer.c:1799 kernel/time/timer.c:2374) run_timer_softirq (kernel/time/timer.c:2405) </IRQ> Kernel panic - not syncing: Fatal exception in interrupt | |
| Title | netfilter: ipset: fix refcount race between list:set GC and swap | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
|
Projects
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MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-08-26T14:36:57.164Z
Reserved: 2026-08-15T05:44:03.931Z
Link: CVE-2026-74748
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-08-26T15:16:53.770
Modified: 2026-08-26T15:16:53.770
Link: CVE-2026-74748
Redhat
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OpenCVE Enrichment
Updated: 2026-08-26T17:00:04Z
Weaknesses