CVE-2026-46319

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Source
https://cve.org/CVERecord?id=CVE-2026-46319
Import Source
https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-46319.json
JSON Data
https://api.test.osv.dev/v1/vulns/CVE-2026-46319
Downstream
Related
Published
2026-06-09T12:11:12Z
Modified
2026-08-31T18:27:02Z
Severity
  • 7.8 (High) CVSS_V3 - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H CVSS Calculator
Summary
net/sched: act_ct: Only release RCU read lock after ct_ft
Details

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 zdi-disclosures@trendmicro.com: 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]

Database specific 
{
    "cna_assigner":  "Linux",
    "osv_generated_from":  "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/46xxx/CVE-2026-46319.json"
}
References

Affected packages

Git / git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git

Affected ranges

Type
GIT
Repo
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Events
Introduced
138470a9b2cc2e26e6018300394afc3858a54e6a
Fixed
ece578ca61e572df96cfc80456357ebfae0b4b9e
Fixed
a2e0c045c87aa252eb61412e67dd91f2c2b19f81
Fixed
67c9ecc9f2575273ed1323e312881fc98ac83d6d
Fixed
f23424a0ddadb494d4bd57056a7ca703312d3a7b
Fixed
17dfb67cb399b660105d9a8c6100851c0d0cdc70
Fixed
4c727c6967a41b37efe0f26332ca9ec5b74785a3
Fixed
3e20e1b3058e0b94638e7b931c138e840e266724
Fixed
f462dca0c8415bf0058d0ffa476354c4476d0f09

Database specific

source 
"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-46319.json"

Linux / Kernel

Package

Name
Kernel

Affected ranges

Type
ECOSYSTEM
Events
Introduced
5.7.0
Fixed
5.10.258
Type
ECOSYSTEM
Events
Introduced
5.11.0
Fixed
5.15.209
Type
ECOSYSTEM
Events
Introduced
5.16.0
Fixed
6.1.175
Type
ECOSYSTEM
Events
Introduced
6.2.0
Fixed
6.6.141
Type
ECOSYSTEM
Events
Introduced
6.7.0
Fixed
6.12.91
Type
ECOSYSTEM
Events
Introduced
6.13.0
Fixed
6.18.33
Type
ECOSYSTEM
Events
Introduced
6.19.0
Fixed
7.0.10

Database specific

source 
"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-46319.json"