{"document":{"category":"csaf_vex","csaf_version":"2.0","title":"CVE-2026-46319: net/sched: act_ct: Only release RCU read lock after ct_ft","publisher":{"category":"vendor","name":"HarborGuard Database","namespace":"https://database.harborguard.co"},"tracking":{"id":"CVE-2026-46319","status":"final","version":"1","initial_release_date":"2026-06-09T12:11:12.128Z","current_release_date":"2026-06-14T04:30:13.452Z","revision_history":[{"date":"2026-06-09T12:11:12.128Z","number":"1","summary":"Initial machine-readable export from HarborGuard."}]},"distribution":{"tlp":{"label":"WHITE"},"text":"Public CVE data; freely redistributable."},"notes":[{"category":"description","text":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: act_ct: Only release RCU read lock after ct_ft\n\nWhen looking up a flow table in act_ct in tcf_ct_flow_table_get(),\nrhashtable_lookup_fast() internally opens and closes an RCU read critical\nsection before returning ct_ft.\nThe tcf_ct_flow_table_cleanup_work() can complete before refcount_inc_not_zero()\nis invoked on the returned ct_ft resulting in a UAF on the already freed ct_ft\nobject. This vulnerability can lead to privilege escalation.\n\nAnalysis from zdi-disclosures@trendmicro.com:\nWhen initializing act_ct, tcf_ct_init() is called, which internally triggers\ntcf_ct_flow_table_get().\n\nstatic int tcf_ct_flow_table_get(struct net *net, struct tcf_ct_params *params)\n\n{\n                struct zones_ht_key key = { .net = net, .zone = params->zone };\n                struct tcf_ct_flow_table *ct_ft;\n                int err = -ENOMEM;\n\n                mutex_lock(&zones_mutex);\n                ct_ft = rhashtable_lookup_fast(&zones_ht, &key, zones_params); // [1]\n                if (ct_ft && refcount_inc_not_zero(&ct_ft->ref)) // [2]\n                                goto out_unlock;\n                ...\n}\n\nstatic __always_inline void *rhashtable_lookup_fast(\n                struct rhashtable *ht, const void *key,\n                const struct rhashtable_params params)\n{\n                void *obj;\n\n                rcu_read_lock();\n                obj = rhashtable_lookup(ht, key, params);\n                rcu_read_unlock();\n\n                return obj;\n}\n\nAt [1], rhashtable_lookup_fast() looks up and returns the corresponding ct_ft\nfrom zones_ht . The lookup is performed within an RCU read critical section\nthrough rcu_read_lock() / rcu_read_unlock(), which prevents the object from\nbeing freed. However, at the point of function return, rcu_read_unlock() has\nalready been called, and there is nothing preventing ct_ft from being freed\nbefore reaching refcount_inc_not_zero(&ct_ft->ref) at [2]. This interval becomes\nthe race window, during which ct_ft can be freed.\n\nFree Process:\n\ntcf_ct_flow_table_put() is executed through the path tcf_ct_cleanup() call_rcu()\ntcf_ct_params_free_rcu() tcf_ct_params_free() tcf_ct_flow_table_put().\n\nstatic void tcf_ct_flow_table_put(struct tcf_ct_flow_table *ct_ft)\n{\n                if (refcount_dec_and_test(&ct_ft->ref)) {\n                                rhashtable_remove_fast(&zones_ht, &ct_ft->node, zones_params);\n                                INIT_RCU_WORK(&ct_ft->rwork, tcf_ct_flow_table_cleanup_work); // [3]\n                                queue_rcu_work(act_ct_wq, &ct_ft->rwork);\n                }\n}\n\nAt [3], tcf_ct_flow_table_cleanup_work() is scheduled as RCU work\n\nstatic void tcf_ct_flow_table_cleanup_work(struct work_struct *work)\n\n{\n                struct tcf_ct_flow_table *ct_ft;\n                struct flow_block *block;\n\n                ct_ft = container_of(to_rcu_work(work), struct tcf_ct_flow_table,\n                                                                rwork);\n                nf_flow_table_free(&ct_ft->nf_ft);\n                block = &ct_ft->nf_ft.flow_block;\n                down_write(&ct_ft->nf_ft.flow_block_lock);\n                WARN_ON(!list_empty(&block->cb_list));\n                up_write(&ct_ft->nf_ft.flow_block_lock);\n                kfree(ct_ft); // [4]\n\n                module_put(THIS_MODULE);\n}\n\ntcf_ct_flow_table_cleanup_work() frees ct_ft at [4]. When this function executes\nbetween [1] and [2], UAF occurs.\n\nThis race condition has a very short race window, making it generally\ndifficult to trigger. Therefore, to trigger the vulnerability an msleep(100) was\ninserted after[1]","title":"CVE description"}],"references":[{"category":"self","summary":"CVE-2026-46319 on HarborGuard Database","url":"https://database.harborguard.co/cve/CVE-2026-46319"},{"category":"external","summary":"CVE Record","url":"https://www.cve.org/CVERecord?id=CVE-2026-46319"},{"category":"external","summary":"git.kernel.org","url":"https://git.kernel.org/stable/c/ece578ca61e572df96cfc80456357ebfae0b4b9e"},{"category":"external","summary":"git.kernel.org","url":"https://git.kernel.org/stable/c/a2e0c045c87aa252eb61412e67dd91f2c2b19f81"},{"category":"external","summary":"git.kernel.org","url":"https://git.kernel.org/stable/c/67c9ecc9f2575273ed1323e312881fc98ac83d6d"},{"category":"external","summary":"git.kernel.org","url":"https://git.kernel.org/stable/c/f23424a0ddadb494d4bd57056a7ca703312d3a7b"},{"category":"external","summary":"git.kernel.org","url":"https://git.kernel.org/stable/c/17dfb67cb399b660105d9a8c6100851c0d0cdc70"},{"category":"external","summary":"git.kernel.org","url":"https://git.kernel.org/stable/c/4c727c6967a41b37efe0f26332ca9ec5b74785a3"},{"category":"external","summary":"git.kernel.org","url":"https://git.kernel.org/stable/c/3e20e1b3058e0b94638e7b931c138e840e266724"},{"category":"external","summary":"git.kernel.org","url":"https://git.kernel.org/stable/c/f462dca0c8415bf0058d0ffa476354c4476d0f09"}]},"product_tree":{"branches":[{"category":"vendor","name":"Linux","branches":[{"category":"product_name","name":"Linux","branches":[{"category":"product_version_range","name":">=138470a9b2cc2e26e6018300394afc3858a54e6a 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<67c9ecc9f2575273ed1323e312881fc98ac83d6d","product_id":"CSAFPID-3","product_identification_helper":{"cpe":"cpe:2.3:a:linux:linux:*:*:*:*:*:*:*:*"}}},{"category":"product_version_range","name":">=138470a9b2cc2e26e6018300394afc3858a54e6a <f23424a0ddadb494d4bd57056a7ca703312d3a7b","product":{"name":"Linux Linux >=138470a9b2cc2e26e6018300394afc3858a54e6a <f23424a0ddadb494d4bd57056a7ca703312d3a7b","product_id":"CSAFPID-4","product_identification_helper":{"cpe":"cpe:2.3:a:linux:linux:*:*:*:*:*:*:*:*"}}},{"category":"product_version_range","name":">=138470a9b2cc2e26e6018300394afc3858a54e6a <17dfb67cb399b660105d9a8c6100851c0d0cdc70","product":{"name":"Linux Linux >=138470a9b2cc2e26e6018300394afc3858a54e6a <17dfb67cb399b660105d9a8c6100851c0d0cdc70","product_id":"CSAFPID-5","product_identification_helper":{"cpe":"cpe:2.3:a:linux:linux:*:*:*:*:*:*:*:*"}}},{"category":"product_version_range","name":">=138470a9b2cc2e26e6018300394afc3858a54e6a <4c727c6967a41b37efe0f26332ca9ec5b74785a3","product":{"name":"Linux Linux >=138470a9b2cc2e26e6018300394afc3858a54e6a <4c727c6967a41b37efe0f26332ca9ec5b74785a3","product_id":"CSAFPID-6","product_identification_helper":{"cpe":"cpe:2.3:a:linux:linux:*:*:*:*:*:*:*:*"}}},{"category":"product_version_range","name":">=138470a9b2cc2e26e6018300394afc3858a54e6a <3e20e1b3058e0b94638e7b931c138e840e266724","product":{"name":"Linux Linux >=138470a9b2cc2e26e6018300394afc3858a54e6a <3e20e1b3058e0b94638e7b931c138e840e266724","product_id":"CSAFPID-7","product_identification_helper":{"cpe":"cpe:2.3:a:linux:linux:*:*:*:*:*:*:*:*"}}},{"category":"product_version_range","name":">=138470a9b2cc2e26e6018300394afc3858a54e6a <f462dca0c8415bf0058d0ffa476354c4476d0f09","product":{"name":"Linux Linux >=138470a9b2cc2e26e6018300394afc3858a54e6a <f462dca0c8415bf0058d0ffa476354c4476d0f09","product_id":"CSAFPID-8","product_identification_helper":{"cpe":"cpe:2.3:a:linux:linux:*:*:*:*:*:*:*:*"}}}]}]},{"category":"vendor","name":"Linux","branches":[{"category":"product_name","name":"Linux","branches":[{"category":"product_version","name":"5.7","product":{"name":"Linux Linux 5.7","product_id":"CSAFPID-9","product_identification_helper":{"cpe":"cpe:2.3:a:linux:linux:5.7:*:*:*:*:*:*:*"}}},{"category":"product_version","name":"0","product":{"name":"Linux Linux 0","product_id":"CSAFPID-10","product_identification_helper":{"cpe":"cpe:2.3:a:linux:linux:5.7:*:*:*:*:*:*:*"}}},{"category":"product_version","name":"5.10.258","product":{"name":"Linux Linux 5.10.258","product_id":"CSAFPID-11","product_identification_helper":{"cpe":"cpe:2.3:a:linux:linux:5.7:*:*:*:*:*:*:*"}}},{"category":"product_version","name":"5.15.209","product":{"name":"Linux Linux 5.15.209","product_id":"CSAFPID-12","product_identification_helper":{"cpe":"cpe:2.3:a:linux:linux:5.7:*:*:*:*:*:*:*"}}},{"category":"product_version","name":"6.1.175","product":{"name":"Linux Linux 6.1.175","product_id":"CSAFPID-13","product_identification_helper":{"cpe":"cpe:2.3:a:linux:linux:5.7:*:*:*:*:*:*:*"}}},{"category":"product_version","name":"6.6.141","product":{"name":"Linux Linux 6.6.141","product_id":"CSAFPID-14","product_identification_helper":{"cpe":"cpe:2.3:a:linux:linux:5.7:*:*:*:*:*:*:*"}}},{"category":"product_version","name":"6.12.91","product":{"name":"Linux Linux 6.12.91","product_id":"CSAFPID-15","product_identification_helper":{"cpe":"cpe:2.3:a:linux:linux:5.7:*:*:*:*:*:*:*"}}},{"category":"product_version","name":"6.18.33","product":{"name":"Linux Linux 6.18.33","product_id":"CSAFPID-16","product_identification_helper":{"cpe":"cpe:2.3:a:linux:linux:5.7:*:*:*:*:*:*:*"}}},{"category":"product_version","name":"7.0.10","product":{"name":"Linux Linux 7.0.10","product_id":"CSAFPID-17","product_identification_helper":{"cpe":"cpe:2.3:a:linux:linux:5.7:*:*:*:*:*:*:*"}}},{"category":"product_version","name":"7.1-rc1","product":{"name":"Linux Linux 7.1-rc1","product_id":"CSAFPID-18","product_identification_helper":{"cpe":"cpe:2.3:a:linux:linux:5.7:*:*:*:*:*:*:*"}}}]}]}]},"vulnerabilities":[{"cve":"CVE-2026-46319","title":"net/sched: act_ct: Only release RCU read lock after ct_ft","notes":[{"category":"description","text":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: act_ct: Only release RCU read lock after ct_ft\n\nWhen looking up a flow table in act_ct in tcf_ct_flow_table_get(),\nrhashtable_lookup_fast() internally opens and closes an RCU read critical\nsection before returning ct_ft.\nThe tcf_ct_flow_table_cleanup_work() can complete before refcount_inc_not_zero()\nis invoked on the returned ct_ft resulting in a UAF on the already freed ct_ft\nobject. This vulnerability can lead to privilege escalation.\n\nAnalysis from zdi-disclosures@trendmicro.com:\nWhen initializing act_ct, tcf_ct_init() is called, which internally triggers\ntcf_ct_flow_table_get().\n\nstatic int tcf_ct_flow_table_get(struct net *net, struct tcf_ct_params *params)\n\n{\n                struct zones_ht_key key = { .net = net, .zone = params->zone };\n                struct tcf_ct_flow_table *ct_ft;\n                int err = -ENOMEM;\n\n                mutex_lock(&zones_mutex);\n                ct_ft = rhashtable_lookup_fast(&zones_ht, &key, zones_params); // [1]\n                if (ct_ft && refcount_inc_not_zero(&ct_ft->ref)) // [2]\n                                goto out_unlock;\n                ...\n}\n\nstatic __always_inline void *rhashtable_lookup_fast(\n                struct rhashtable *ht, const void *key,\n                const struct rhashtable_params params)\n{\n                void *obj;\n\n                rcu_read_lock();\n                obj = rhashtable_lookup(ht, key, params);\n                rcu_read_unlock();\n\n                return obj;\n}\n\nAt [1], rhashtable_lookup_fast() looks up and returns the corresponding ct_ft\nfrom zones_ht . The lookup is performed within an RCU read critical section\nthrough rcu_read_lock() / rcu_read_unlock(), which prevents the object from\nbeing freed. However, at the point of function return, rcu_read_unlock() has\nalready been called, and there is nothing preventing ct_ft from being freed\nbefore reaching refcount_inc_not_zero(&ct_ft->ref) at [2]. This interval becomes\nthe race window, during which ct_ft can be freed.\n\nFree Process:\n\ntcf_ct_flow_table_put() is executed through the path tcf_ct_cleanup() call_rcu()\ntcf_ct_params_free_rcu() tcf_ct_params_free() tcf_ct_flow_table_put().\n\nstatic void tcf_ct_flow_table_put(struct tcf_ct_flow_table *ct_ft)\n{\n                if (refcount_dec_and_test(&ct_ft->ref)) {\n                                rhashtable_remove_fast(&zones_ht, &ct_ft->node, zones_params);\n                                INIT_RCU_WORK(&ct_ft->rwork, tcf_ct_flow_table_cleanup_work); // [3]\n                                queue_rcu_work(act_ct_wq, &ct_ft->rwork);\n                }\n}\n\nAt [3], tcf_ct_flow_table_cleanup_work() is scheduled as RCU work\n\nstatic void tcf_ct_flow_table_cleanup_work(struct work_struct *work)\n\n{\n                struct tcf_ct_flow_table *ct_ft;\n                struct flow_block *block;\n\n                ct_ft = container_of(to_rcu_work(work), struct tcf_ct_flow_table,\n                                                                rwork);\n                nf_flow_table_free(&ct_ft->nf_ft);\n                block = &ct_ft->nf_ft.flow_block;\n                down_write(&ct_ft->nf_ft.flow_block_lock);\n                WARN_ON(!list_empty(&block->cb_list));\n                up_write(&ct_ft->nf_ft.flow_block_lock);\n                kfree(ct_ft); // [4]\n\n                module_put(THIS_MODULE);\n}\n\ntcf_ct_flow_table_cleanup_work() frees ct_ft at [4]. When this function executes\nbetween [1] and [2], UAF occurs.\n\nThis race condition has a very short race window, making it generally\ndifficult to trigger. Therefore, to trigger the vulnerability an msleep(100) was\ninserted after[1]","title":"CVE description"}],"product_status":{"known_affected":["CSAFPID-1","CSAFPID-2","CSAFPID-3","CSAFPID-4","CSAFPID-5","CSAFPID-6","CSAFPID-7","CSAFPID-8","CSAFPID-9"],"fixed":["CSAFPID-10","CSAFPID-11","CSAFPID-12","CSAFPID-13","CSAFPID-14","CSAFPID-15","CSAFPID-16","CSAFPID-17","CSAFPID-18"]},"scores":[{"cvss_v3":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH"},"products":["CSAFPID-1","CSAFPID-2","CSAFPID-3","CSAFPID-4","CSAFPID-5","CSAFPID-6","CSAFPID-7","CSAFPID-8","CSAFPID-9"]}],"remediations":[{"category":"vendor_fix","details":"Update to a fixed version: 0, 17dfb67cb399b660105d9a8c6100851c0d0cdc70, 3e20e1b3058e0b94638e7b931c138e840e266724, 4c727c6967a41b37efe0f26332ca9ec5b74785a3, 5.10.258, 5.15.209, 6.1.175, 6.6.141, 6.12.91, 6.18.33, 67c9ecc9f2575273ed1323e312881fc98ac83d6d, 7.0.10, 7.1-rc1, a2e0c045c87aa252eb61412e67dd91f2c2b19f81, ece578ca61e572df96cfc80456357ebfae0b4b9e, f23424a0ddadb494d4bd57056a7ca703312d3a7b, f462dca0c8415bf0058d0ffa476354c4476d0f09.","product_ids":["CSAFPID-1","CSAFPID-2","CSAFPID-3","CSAFPID-4","CSAFPID-5","CSAFPID-6","CSAFPID-7","CSAFPID-8","CSAFPID-9"]}]}]}