CVE-2026-74660
Received Received - Intake

Use-After-Free in Linux Kernel ebt_nflog

Publication date: 2026-08-22

Last updated on: 2026-08-22

Assigner: kernel.org

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.

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Meta Information

Published
2026-08-22
Last Modified
2026-08-22
Generated
2026-08-22
AI Q&A
2026-08-22
EPSS Evaluated
N/A
NVD
CVE-2026-74660
EUVD
EUVD-2026-64347

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
netfilter ebt_nflog *

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This is a use-after-free vulnerability in the Linux kernel's netfilter subsystem. It occurs in the ebt_nflog module when the nfnetlink_log module is unloaded while an ebtables nflog rule is still active. The issue arises because ebt_nflog does not hold a reference to the logger module, allowing it to access freed memory when the module is unloaded.

Detection Guidance

This vulnerability involves a use-after-free issue in the Linux kernel's ebt_nflog module. Detection requires checking for kernel logs indicating slab-use-after-free errors related to nfnetlink_log or ebt_nflog. Monitor system logs for KASAN reports or kernel panics involving these components.

Impact Analysis

This vulnerability could lead to system crashes, kernel memory corruption, or potential privilege escalation if exploited. Attackers could trigger a use-after-free condition, causing denial-of-service or arbitrary code execution in the kernel.

Mitigation Strategies

Apply the latest kernel security patches that address this issue. If patches are unavailable, consider disabling ebtables nflog rules temporarily until a fix is applied. Monitor kernel logs for signs of exploitation or crashes.

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