In the Linux kernel, the following vulnerability has been resolved:
netfilter: ebt_nflog: pin the NFLOG backend
nf_log_unregister() runs after the per-net teardown so its final RCU
grace period also drains readers that obtained the logger from a per-net
binding. However, ebt_nflog passes an explicit ULOG log type to
nf_log_packet() without holding a reference on the selected logger module,
unlike the xt_NFLOG and nft_log frontends.
An ebtables nflog rule can therefore remain callable while nfnetlink_log
is unloaded. The resulting interleaving is:
CPU 0 CPU 1
nfnetlink_log_fini()
unregister_pernet_subsys()
kfree(nfnl_log_pernet(net))
ebt_nflog_tg()
nf_log_packet()
nfulnl_log_packet()
instance_lookup_get_rcu()
The global ULOG logger is still registered at this point, so CPU 1
dereferences the per-net state after CPU 0 has freed it. KASAN reported:
BUG: KASAN: slab-use-after-free in instance_lookup_get_rcu
Read of size 8 at addr ff110001052e6210 by task poc/92
Call Trace:
instance_lookup_get_rcu+0x1ce/0x1f0 [nfnetlink_log]
nfulnl_log_packet+0x248/0x2fb0 [nfnetlink_log]
nf_log_packet+0x204/0x300
ebt_nflog_tg+0x351/0x550
ebt_do_table+0xedf/0x22b0
Allocated by task 90:
__kmalloc_noprof+0x186/0x470
ops_init+0x6d/0x420
register_pernet_operations+0x2f6/0x670
register_pernet_subsys+0x23/0x40
Freed by task 93:
kfree+0x131/0x3c0
ops_undo_list+0x3e3/0x700
unregister_pernet_operations+0x232/0x490
unregister_pernet_subsys+0x1c/0x30
nfnetlink_log_fini+0x34/0x450 [nfnetlink_log]
Acquire the ULOG logger module reference when an ebt_nflog rule is
validated and release it when the rule is destroyed. Request the NFLOG
backend for legacy callers when needed, matching xt_NFLOG. This prevents
module teardown until all ebt_nflog rules have stopped using the logger.
netfilter: ebt_nflog: pin the NFLOG backend
nf_log_unregister() runs after the per-net teardown so its final RCU
grace period also drains readers that obtained the logger from a per-net
binding. However, ebt_nflog passes an explicit ULOG log type to
nf_log_packet() without holding a reference on the selected logger module,
unlike the xt_NFLOG and nft_log frontends.
An ebtables nflog rule can therefore remain callable while nfnetlink_log
is unloaded. The resulting interleaving is:
CPU 0 CPU 1
nfnetlink_log_fini()
unregister_pernet_subsys()
kfree(nfnl_log_pernet(net))
ebt_nflog_tg()
nf_log_packet()
nfulnl_log_packet()
instance_lookup_get_rcu()
The global ULOG logger is still registered at this point, so CPU 1
dereferences the per-net state after CPU 0 has freed it. KASAN reported:
BUG: KASAN: slab-use-after-free in instance_lookup_get_rcu
Read of size 8 at addr ff110001052e6210 by task poc/92
Call Trace:
instance_lookup_get_rcu+0x1ce/0x1f0 [nfnetlink_log]
nfulnl_log_packet+0x248/0x2fb0 [nfnetlink_log]
nf_log_packet+0x204/0x300
ebt_nflog_tg+0x351/0x550
ebt_do_table+0xedf/0x22b0
Allocated by task 90:
__kmalloc_noprof+0x186/0x470
ops_init+0x6d/0x420
register_pernet_operations+0x2f6/0x670
register_pernet_subsys+0x23/0x40
Freed by task 93:
kfree+0x131/0x3c0
ops_undo_list+0x3e3/0x700
unregister_pernet_operations+0x232/0x490
unregister_pernet_subsys+0x1c/0x30
nfnetlink_log_fini+0x34/0x450 [nfnetlink_log]
Acquire the ULOG logger module reference when an ebt_nflog rule is
validated and release it when the rule is destroyed. Request the NFLOG
backend for legacy callers when needed, matching xt_NFLOG. This prevents
module teardown until all ebt_nflog rules have stopped using the logger.
Metrics
Affected Vendors & Products
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Fixes
Solution
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Workaround
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References
History
Sat, 22 Aug 2026 18:15:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Weaknesses | CWE-416 |
Sat, 22 Aug 2026 15:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: netfilter: ebt_nflog: pin the NFLOG backend nf_log_unregister() runs after the per-net teardown so its final RCU grace period also drains readers that obtained the logger from a per-net binding. However, ebt_nflog passes an explicit ULOG log type to nf_log_packet() without holding a reference on the selected logger module, unlike the xt_NFLOG and nft_log frontends. An ebtables nflog rule can therefore remain callable while nfnetlink_log is unloaded. The resulting interleaving is: CPU 0 CPU 1 nfnetlink_log_fini() unregister_pernet_subsys() kfree(nfnl_log_pernet(net)) ebt_nflog_tg() nf_log_packet() nfulnl_log_packet() instance_lookup_get_rcu() The global ULOG logger is still registered at this point, so CPU 1 dereferences the per-net state after CPU 0 has freed it. KASAN reported: BUG: KASAN: slab-use-after-free in instance_lookup_get_rcu Read of size 8 at addr ff110001052e6210 by task poc/92 Call Trace: instance_lookup_get_rcu+0x1ce/0x1f0 [nfnetlink_log] nfulnl_log_packet+0x248/0x2fb0 [nfnetlink_log] nf_log_packet+0x204/0x300 ebt_nflog_tg+0x351/0x550 ebt_do_table+0xedf/0x22b0 Allocated by task 90: __kmalloc_noprof+0x186/0x470 ops_init+0x6d/0x420 register_pernet_operations+0x2f6/0x670 register_pernet_subsys+0x23/0x40 Freed by task 93: kfree+0x131/0x3c0 ops_undo_list+0x3e3/0x700 unregister_pernet_operations+0x232/0x490 unregister_pernet_subsys+0x1c/0x30 nfnetlink_log_fini+0x34/0x450 [nfnetlink_log] Acquire the ULOG logger module reference when an ebt_nflog rule is validated and release it when the rule is destroyed. Request the NFLOG backend for legacy callers when needed, matching xt_NFLOG. This prevents module teardown until all ebt_nflog rules have stopped using the logger. | |
| Title | netfilter: ebt_nflog: pin the NFLOG backend | |
| 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: 2026-08-22T15:32:33.677Z
Reserved: 2026-08-15T05:44:03.924Z
Link: CVE-2026-74660
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-08-22T16:16:39.743
Modified: 2026-08-22T16:16:39.743
Link: CVE-2026-74660
Redhat
No data.
OpenCVE Enrichment
Updated: 2026-08-22T18:00:04Z
Weaknesses