{"id":"CVE-2026-46319","summary":"net/sched: act_ct: Only release RCU read lock after ct_ft","details":"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-\u003ezone };\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-\u003eref)) // [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-\u003eref) 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-\u003eref)) {\n                                rhashtable_remove_fast(&zones_ht, &ct_ft-\u003enode, zones_params);\n                                INIT_RCU_WORK(&ct_ft-\u003erwork, tcf_ct_flow_table_cleanup_work); // [3]\n                                queue_rcu_work(act_ct_wq, &ct_ft-\u003erwork);\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-\u003enf_ft);\n                block = &ct_ft-\u003enf_ft.flow_block;\n                down_write(&ct_ft-\u003enf_ft.flow_block_lock);\n                WARN_ON(!list_empty(&block-\u003ecb_list));\n                up_write(&ct_ft-\u003enf_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]","modified":"2026-09-15T18:26:44.327456178Z","published":"2026-06-09T12:11:12.128Z","related":["SUSE-SU-2026:22521-1","SUSE-SU-2026:22522-1","SUSE-SU-2026:22665-1","SUSE-SU-2026:22666-1","SUSE-SU-2026:22742-1","SUSE-SU-2026:22769-1","SUSE-SU-2026:22812-1","SUSE-SU-2026:22835-1","SUSE-SU-2026:23258-1","SUSE-SU-2026:23259-1","SUSE-SU-2026:23260-1","SUSE-SU-2026:23261-1","SUSE-SU-2026:23262-1","SUSE-SU-2026:23263-1","SUSE-SU-2026:23264-1","SUSE-SU-2026:23265-1","SUSE-SU-2026:23266-1","SUSE-SU-2026:23267-1","SUSE-SU-2026:23268-1","SUSE-SU-2026:23269-1","SUSE-SU-2026:23270-1","SUSE-SU-2026:23271-1","SUSE-SU-2026:23272-1","SUSE-SU-2026:23280-1","SUSE-SU-2026:23281-1","SUSE-SU-2026:23282-1","SUSE-SU-2026:23283-1","SUSE-SU-2026:23284-1","SUSE-SU-2026:23285-1","SUSE-SU-2026:23286-1","SUSE-SU-2026:23287-1","SUSE-SU-2026:23288-1","SUSE-SU-2026:23290-1","SUSE-SU-2026:23291-1","SUSE-SU-2026:23292-1","SUSE-SU-2026:23293-1","SUSE-SU-2026:23295-1","SUSE-SU-2026:23296-1","SUSE-SU-2026:23329-1","SUSE-SU-2026:23330-1","SUSE-SU-2026:23331-1","SUSE-SU-2026:23332-1","SUSE-SU-2026:23333-1","SUSE-SU-2026:23334-1","SUSE-SU-2026:23335-1","SUSE-SU-2026:23336-1","SUSE-SU-2026:23337-1","SUSE-SU-2026:23338-1","SUSE-SU-2026:23339-1","SUSE-SU-2026:23340-1","SUSE-SU-2026:23341-1","SUSE-SU-2026:23342-1","SUSE-SU-2026:23343-1","SUSE-SU-2026:23366-1","SUSE-SU-2026:23367-1","SUSE-SU-2026:23368-1","SUSE-SU-2026:23369-1","SUSE-SU-2026:23370-1","SUSE-SU-2026:23371-1","SUSE-SU-2026:23372-1","SUSE-SU-2026:23373-1","SUSE-SU-2026:23374-1","SUSE-SU-2026:23375-1","SUSE-SU-2026:23376-1","SUSE-SU-2026:23377-1","SUSE-SU-2026:23378-1","SUSE-SU-2026:23379-1","SUSE-SU-2026:23380-1","SUSE-SU-2026:23383-1","SUSE-SU-2026:23384-1","SUSE-SU-2026:23385-1","SUSE-SU-2026:23386-1","SUSE-SU-2026:23387-1","SUSE-SU-2026:23388-1","SUSE-SU-2026:23389-1","SUSE-SU-2026:23390-1","SUSE-SU-2026:23416-1","SUSE-SU-2026:23417-1","SUSE-SU-2026:23418-1","SUSE-SU-2026:23419-1","SUSE-SU-2026:23420-1","SUSE-SU-2026:23421-1","SUSE-SU-2026:23422-1","SUSE-SU-2026:23423-1","SUSE-SU-2026:23424-1","SUSE-SU-2026:23425-1","SUSE-SU-2026:23426-1","SUSE-SU-2026:23427-1","SUSE-SU-2026:23428-1","SUSE-SU-2026:23429-1","SUSE-SU-2026:23430-1","SUSE-SU-2026:23431-1","SUSE-SU-2026:23432-1","SUSE-SU-2026:23433-1","SUSE-SU-2026:23434-1","SUSE-SU-2026:23435-1","SUSE-SU-2026:23436-1","SUSE-SU-2026:23437-1","SUSE-SU-2026:23438-1","SUSE-SU-2026:23482-1","SUSE-SU-2026:23483-1","SUSE-SU-2026:23484-1","SUSE-SU-2026:23485-1","SUSE-SU-2026:23486-1","SUSE-SU-2026:23487-1","SUSE-SU-2026:23531-1","SUSE-SU-2026:23532-1","SUSE-SU-2026:23533-1","SUSE-SU-2026:23534-1","SUSE-SU-2026:23535-1","SUSE-SU-2026:23541-1","SUSE-SU-2026:2799-1","SUSE-SU-2026:2800-1","SUSE-SU-2026:2840-1","SUSE-SU-2026:2841-1","SUSE-SU-2026:3044-1","SUSE-SU-2026:3089-1","SUSE-SU-2026:3156-1","SUSE-SU-2026:3689-1","SUSE-SU-2026:3694-1","SUSE-SU-2026:3696-1","SUSE-SU-2026:3697-1","SUSE-SU-2026:3698-1","SUSE-SU-2026:3699-1","SUSE-SU-2026:3700-1","SUSE-SU-2026:3702-1","SUSE-SU-2026:3703-1","SUSE-SU-2026:3704-1","SUSE-SU-2026:3707-1","SUSE-SU-2026:3708-1","SUSE-SU-2026:3709-1","SUSE-SU-2026:3710-1","SUSE-SU-2026:3715-1","SUSE-SU-2026:3717-1","SUSE-SU-2026:3719-1","SUSE-SU-2026:3721-1","SUSE-SU-2026:3722-1","SUSE-SU-2026:3724-1","SUSE-SU-2026:3726-1","SUSE-SU-2026:3728-1","SUSE-SU-2026:3729-1","SUSE-SU-2026:3734-1","SUSE-SU-2026:3739-1","SUSE-SU-2026:3744-1","SUSE-SU-2026:3746-1","SUSE-SU-2026:3747-1","SUSE-SU-2026:3748-1","SUSE-SU-2026:3750-1","SUSE-SU-2026:3754-1","SUSE-SU-2026:3756-1","SUSE-SU-2026:3757-1","SUSE-SU-2026:3759-1","SUSE-SU-2026:3760-1","SUSE-SU-2026:3761-1","SUSE-SU-2026:3766-1","SUSE-SU-2026:3768-1","SUSE-SU-2026:3770-1","SUSE-SU-2026:3771-1","SUSE-SU-2026:3774-1","SUSE-SU-2026:3775-1","SUSE-SU-2026:3776-1","SUSE-SU-2026:3777-1","SUSE-SU-2026:3778-1","SUSE-SU-2026:3779-1","SUSE-SU-2026:3780-1","openSUSE-SU-2026:11014-1","openSUSE-SU-2026:21388-1"],"database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/46xxx/CVE-2026-46319.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/17dfb67cb399b660105d9a8c6100851c0d0cdc70"},{"type":"WEB","url":"https://git.kernel.org/stable/c/3e20e1b3058e0b94638e7b931c138e840e266724"},{"type":"WEB","url":"https://git.kernel.org/stable/c/4c727c6967a41b37efe0f26332ca9ec5b74785a3"},{"type":"WEB","url":"https://git.kernel.org/stable/c/67c9ecc9f2575273ed1323e312881fc98ac83d6d"},{"type":"WEB","url":"https://git.kernel.org/stable/c/a2e0c045c87aa252eb61412e67dd91f2c2b19f81"},{"type":"WEB","url":"https://git.kernel.org/stable/c/ece578ca61e572df96cfc80456357ebfae0b4b9e"},{"type":"WEB","url":"https://git.kernel.org/stable/c/f23424a0ddadb494d4bd57056a7ca703312d3a7b"},{"type":"WEB","url":"https://git.kernel.org/stable/c/f462dca0c8415bf0058d0ffa476354c4476d0f09"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/46xxx/CVE-2026-46319.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-46319"},{"type":"PACKAGE","url":"https://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/cve-osv-conversion/osv-output/CVE-2026-46319.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"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/cve-osv-conversion/osv-output/CVE-2026-46319.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"}]}