CVE-2026-23231
Published: 04 March 2026
Summary
CVE-2026-23231 is a high-severity Use After Free (CWE-416) vulnerability in Linux Linux Kernel. Its CVSS base score is 7.8 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked in the top 28.6% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 SI-2 (Flaw Remediation) and RA-5 (Vulnerability Monitoring and Scanning).
Threat & Defense at a Glance
Threat & Defense Details
Mitigating Controls (NIST 800-53 r5)AI
Timely remediation via kernel patches directly resolves the use-after-free by inserting synchronize_rcu() between chain deletion and destruction.
Kernel memory protection safeguards like KASLR, SMEP, and SMAP hinder exploitation of the use-after-free in nf_tables chain structures.
Vulnerability scanning identifies unpatched kernel versions vulnerable to this netfilter nf_tables race condition.
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Local kernel UAF in nf_tables directly enables privilege escalation via crafted chain registration failure and RCU race exploitation.
NVD Description
In the Linux kernel, the following vulnerability has been resolved: netfilter: nf_tables: fix use-after-free in nf_tables_addchain() nf_tables_addchain() publishes the chain to table->chains via list_add_tail_rcu() (in nft_chain_add()) before registering hooks. If nf_tables_register_hook() then fails, the error path calls nft_chain_del() (list_del_rcu()) followed…
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by nf_tables_chain_destroy() with no RCU grace period in between. This creates two use-after-free conditions: 1) Control-plane: nf_tables_dump_chains() traverses table->chains under rcu_read_lock(). A concurrent dump can still be walking the chain when the error path frees it. 2) Packet path: for NFPROTO_INET, nf_register_net_hook() briefly installs the IPv4 hook before IPv6 registration fails. Packets entering nft_do_chain() via the transient IPv4 hook can still be dereferencing chain->blob_gen_X when the error path frees the chain. Add synchronize_rcu() between nft_chain_del() and the chain destroy so that all RCU readers -- both dump threads and in-flight packet evaluation -- have finished before the chain is freed.
Deeper analysisAI
CVE-2026-23231 is a use-after-free vulnerability in the Linux kernel's netfilter nf_tables subsystem, specifically within the nf_tables_addchain() function. The flaw occurs when a chain is published to the table's chains list via list_add_tail_rcu() before hook registration. If nf_tables_register_hook() fails, the error path invokes nft_chain_del() followed immediately by nf_tables_chain_destroy(), without an RCU grace period. This leads to two use-after-free scenarios: control-plane access during nf_tables_dump_chains() under rcu_read_lock(), and packet-path dereferencing in nft_do_chain() for NFPROTO_INET via a transient IPv4 hook.
A local attacker with low privileges (PR:L) can exploit this vulnerability with low attack complexity and no user interaction required (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H). Exploitation targets the race condition during chain addition failure, potentially allowing arbitrary code execution, data corruption, or denial of service through the freed chain structures accessed by concurrent RCU readers in dumps or packet processing.
The referenced kernel stable patches mitigate the issue by inserting synchronize_rcu() between nft_chain_del() (list_del_rcu()) and nf_tables_chain_destroy(), ensuring all RCU readers—including dump threads and in-flight packet evaluations—complete before freeing the chain. Relevant commits include https://git.kernel.org/stable/c/2a6586ecfa4ce1413daaafee250d2590e05f1a33, https://git.kernel.org/stable/c/2f9a4ffeb763aec822f8ff3d1e82202d27d46d4b, https://git.kernel.org/stable/c/7017745068a9068904e1e7a1b170a5785647cc81, https://git.kernel.org/stable/c/71e99ee20fc3f662555118cf1159443250647533, and https://git.kernel.org/stable/c/dbd0af8083dd201f07c49110b2ee93710abdff28.
Details
- CWE(s)