{ "schema_version": "1.6.1", "id": "RPI-CVE-2026-46319", "modified": "2026-10-07T17:22:01Z", "upstream": [ "CVE-2026-46319" ], "published": "2026-06-09T12:10:32Z", "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->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]", "affected": [ { "package": { "ecosystem": "Raspberry Pi OS:12", "name": "linux" }, "versions": [ "1:6.1.47-1+rpt4" ], "ecosystem_specific": { "binaries": [ { "binary_name": "linux-image-6.1.0-rpi3-rpi-2712", "binary_version": "1:6.1.47-1+rpt4" }, { "binary_name": "linux-image-6.1.0-rpi3-rpi-v6", "binary_version": "1:6.1.47-1+rpt4" }, { "binary_name": "linux-image-6.1.0-rpi3-rpi-v7", "binary_version": "1:6.1.47-1+rpt4" }, { "binary_name": "linux-image-6.1.0-rpi3-rpi-v7l", "binary_version": "1:6.1.47-1+rpt4" }, { "binary_name": "linux-image-6.1.0-rpi3-rpi-v8", "binary_version": "1:6.1.47-1+rpt4" } ] }, "database_specific": { "per_version": { "1:6.1.47-1+rpt4": { "linux_commit": "655fc658a15ae7a6f37103754adb39ba52a9a14e", "upstream_version": "6.1.47", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.1.175", "compiled_filter": false } } } } ], "references": [ { "type": "ADVISORY", "url": "https://www.cve.org/CVERecord?id=CVE-2026-46319" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/ece578ca61e572df96cfc80456357ebfae0b4b9e" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/a2e0c045c87aa252eb61412e67dd91f2c2b19f81" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/67c9ecc9f2575273ed1323e312881fc98ac83d6d" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/f23424a0ddadb494d4bd57056a7ca703312d3a7b" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/17dfb67cb399b660105d9a8c6100851c0d0cdc70" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/4c727c6967a41b37efe0f26332ca9ec5b74785a3" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/3e20e1b3058e0b94638e7b931c138e840e266724" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/f462dca0c8415bf0058d0ffa476354c4476d0f09" } ], "database_specific": { "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git", "upstream_modified": "2026-08-05T13:16:28Z" } }