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Vulnerabilities

CVE-2026-46319 Detail

Received

This CVE record has recently been published to the CVE List and has been included within the NVD dataset.

Description

In the Linux kernel, the following vulnerability has been resolved: net/sched: act_ct: Only release RCU read lock after ct_ft When looking up a flow table in act_ct in tcf_ct_flow_table_get(), rhashtable_lookup_fast() internally opens and closes an RCU read critical section before returning ct_ft. The tcf_ct_flow_table_cleanup_work() can complete before refcount_inc_not_zero() is invoked on the returned ct_ft resulting in a UAF on the already freed ct_ft object. This vulnerability can lead to privilege escalation. Analysis from [email protected]: When initializing act_ct, tcf_ct_init() is called, which internally triggers tcf_ct_flow_table_get(). static int tcf_ct_flow_table_get(struct net *net, struct tcf_ct_params *params) { struct zones_ht_key key = { .net = net, .zone = params->zone }; struct tcf_ct_flow_table *ct_ft; int err = -ENOMEM; mutex_lock(&zones_mutex); ct_ft = rhashtable_lookup_fast(&zones_ht, &key, zones_params); // [1] if (ct_ft && refcount_inc_not_zero(&ct_ft->ref)) // [2] goto out_unlock; ... } static __always_inline void *rhashtable_lookup_fast( struct rhashtable *ht, const void *key, const struct rhashtable_params params) { void *obj; rcu_read_lock(); obj = rhashtable_lookup(ht, key, params); rcu_read_unlock(); return obj; } At [1], rhashtable_lookup_fast() looks up and returns the corresponding ct_ft from zones_ht . The lookup is performed within an RCU read critical section through rcu_read_lock() / rcu_read_unlock(), which prevents the object from being freed. However, at the point of function return, rcu_read_unlock() has already been called, and there is nothing preventing ct_ft from being freed before reaching refcount_inc_not_zero(&ct_ft->ref) at [2]. This interval becomes the race window, during which ct_ft can be freed. Free Process: tcf_ct_flow_table_put() is executed through the path tcf_ct_cleanup() call_rcu() tcf_ct_params_free_rcu() tcf_ct_params_free() tcf_ct_flow_table_put(). static void tcf_ct_flow_table_put(struct tcf_ct_flow_table *ct_ft) { if (refcount_dec_and_test(&ct_ft->ref)) { rhashtable_remove_fast(&zones_ht, &ct_ft->node, zones_params); INIT_RCU_WORK(&ct_ft->rwork, tcf_ct_flow_table_cleanup_work); // [3] queue_rcu_work(act_ct_wq, &ct_ft->rwork); } } At [3], tcf_ct_flow_table_cleanup_work() is scheduled as RCU work static void tcf_ct_flow_table_cleanup_work(struct work_struct *work) { struct tcf_ct_flow_table *ct_ft; struct flow_block *block; ct_ft = container_of(to_rcu_work(work), struct tcf_ct_flow_table, rwork); nf_flow_table_free(&ct_ft->nf_ft); block = &ct_ft->nf_ft.flow_block; down_write(&ct_ft->nf_ft.flow_block_lock); WARN_ON(!list_empty(&block->cb_list)); up_write(&ct_ft->nf_ft.flow_block_lock); kfree(ct_ft); // [4] module_put(THIS_MODULE); } tcf_ct_flow_table_cleanup_work() frees ct_ft at [4]. When this function executes between [1] and [2], UAF occurs. This race condition has a very short race window, making it generally difficult to trigger. Therefore, to trigger the vulnerability an msleep(100) was inserted after[1]

Metrics

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CVSS 4.0 Severity and Vector Strings:

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URL	Source(s)	Tag(s)
https://git.kernel.org/stable/c/17dfb67cb399b660105d9a8c6100851c0d0cdc70	kernel.org
https://git.kernel.org/stable/c/3e20e1b3058e0b94638e7b931c138e840e266724	kernel.org
https://git.kernel.org/stable/c/4c727c6967a41b37efe0f26332ca9ec5b74785a3	kernel.org
https://git.kernel.org/stable/c/67c9ecc9f2575273ed1323e312881fc98ac83d6d	kernel.org
https://git.kernel.org/stable/c/a2e0c045c87aa252eb61412e67dd91f2c2b19f81	kernel.org
https://git.kernel.org/stable/c/ece578ca61e572df96cfc80456357ebfae0b4b9e	kernel.org
https://git.kernel.org/stable/c/f23424a0ddadb494d4bd57056a7ca703312d3a7b	kernel.org
https://git.kernel.org/stable/c/f462dca0c8415bf0058d0ffa476354c4476d0f09	kernel.org

Weakness Enumeration

CWE-ID	CWE Name	Source

Change History

3 change records found show changes

New CVE Received from kernel.org 6/09/2026 9:16:37 AM

Action	Type	Old Value
Added	Description	Record truncated, showing 2048 of 3667 characters. View Entire Change Record In the Linux kernel, the following vulnerability has been resolved: net/sched: act_ct: Only release RCU read lock after ct_ft When looking up a flow table in act_ct in tcf_ct_flow_table_get(), rhashtable_lookup_fast() internally opens and closes an RCU read critical section before returning ct_ft. The tcf_ct_flow_table_cleanup_work() can complete before refcount_inc_not_zero() is invoked on the returned ct_ft resulting in a UAF on the already freed ct_ft object. This vulnerability can lead to privilege escalation. Analysis from [email protected]: When initializing act_ct, tcf_ct_init() is called, which internally triggers tcf_ct_flow_table_get(). static int tcf_ct_flow_table_get(struct net net, struct tcf_ct_params params) { struct zones_ht_key key = { .net = net, .zone = params->zone }; struct tcf_ct_flow_table ct_ft; int err = -ENOMEM; mutex_lock(&zones_mutex); ct_ft = rhashtable_lookup_fast(&zones_ht, &key, zones_params); // [1] if (ct_ft && refcount_inc_not_zero(&ct_ft->ref)) // [2] goto out_unlock; ... } static __always_inline void rhashtable_lookup_fast( struct rhashtable ht, const void key, const struct rhashtable_params params) { void *obj; rcu_read_lock(); obj = rhashtable_lookup(ht, key, params); rcu_read_unlock(); return obj; } At [1], rhashtable_lookup_fast() looks up and returns the corresponding ct_ft from zones_ht . The lookup is performed within an RCU read critical section through rcu_read_lock() / rcu_read_unlock(), which prevents the object from being freed. However, at the point of function return, rcu_read_unlock() has already been called, and there is nothing preventing ct_ft from being freed before reaching refcount_inc_not_zero(&ct_ft->ref) at [2]. This interval becomes the race window, during which ct_ft can
Added	Reference	https://git.kernel.org/stable/c/17dfb67cb399b660105d9a8c6100851c0d0cdc70
Added	Reference	https://git.kernel.org/stable/c/3e20e1b3058e0b94638e7b931c138e840e266724
Added	Reference	https://git.kernel.org/stable/c/4c727c6967a41b37efe0f26332ca9ec5b74785a3
Added	Reference	https://git.kernel.org/stable/c/67c9ecc9f2575273ed1323e312881fc98ac83d6d
Added	Reference	https://git.kernel.org/stable/c/a2e0c045c87aa252eb61412e67dd91f2c2b19f81
Added	Reference	https://git.kernel.org/stable/c/ece578ca61e572df96cfc80456357ebfae0b4b9e
Added	Reference	https://git.kernel.org/stable/c/f23424a0ddadb494d4bd57056a7ca703312d3a7b
Added	Reference	https://git.kernel.org/stable/c/f462dca0c8415bf0058d0ffa476354c4476d0f09

Quick Info

CVE Dictionary Entry:
CVE-2026-46319
NVD Published Date:
06/09/2026
NVD Last Modified:
06/17/2026
Source:
kernel.org

URL: https://nvd.nist.gov/vuln/detail/CVE-2026-46319

⇱ NVD - CVE-2026-46319