{"id":"CVE-2024-41010","url":"https://www.cyber-defence.io/tools/cve/CVE-2024-41010","generatedAt":"2026-10-27T23:56:07.700Z","title":"In the Linux kernel, the following vulnerability has been resolved: bpf: Fix too early release of tcx_entry Pedro Pinto and later independently also Hyunwoo Kim and Wongi Lee reported an issue that the tcx_entry can be released too early leading to a…","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Fix too early release of tcx_entry\n\nPedro Pinto and later independently also Hyunwoo Kim and Wongi Lee reported\nan issue that the tcx_entry can be released too early leading to a use\nafter free (UAF) when an active old-style ingress or clsact qdisc with a\nshared tc block is later replaced by another ingress or clsact instance.\n\nEssentially, the sequence to trigger the UAF (one example) can be as follows:\n\n  1. A network namespace is created\n  2. An ingress qdisc is created. This allocates a tcx_entry, and\n     &tcx_entry->miniq is stored in the qdisc's miniqp->p_miniq. At the\n     same time, a tcf block with index 1 is created.\n  3. chain0 is attached to the tcf block. chain0 must be connected to\n     the block linked to the ingress qdisc to later reach the function\n     tcf_chain0_head_change_cb_del() which triggers the UAF.\n  4. Create and graft a clsact qdisc. This causes the ingress qdisc\n     created in step 1 to be removed, thus freeing the previously linked\n     tcx_entry:\n\n     rtnetlink_rcv_msg()\n       => tc_modify_qdisc()\n         => qdisc_create()\n           => clsact_init() [a]\n         => qdisc_graft()\n           => qdisc_destroy()\n             => __qdisc_destroy()\n               => ingress_destroy() [b]\n                 => tcx_entry_free()\n                   => kfree_rcu() // tcx_entry freed\n\n  5. Finally, the network namespace is closed. This registers the\n     cleanup_net worker, and during the process of releasing the\n     remaining clsact qdisc, it accesses the tcx_entry that was\n     already freed in step 4, causing the UAF to occur:\n\n     cleanup_net()\n       => ops_exit_list()\n         => default_device_exit_batch()\n           => unregister_netdevice_many()\n             => unregister_netdevice_many_notify()\n               => dev_shutdown()\n                 => qdisc_put()\n                   => clsact_destroy() [c]\n                     => tcf_block_put_ext()\n                       => tcf_chain0_head_change_cb_del()\n                         => tcf_chain_head_change_item()\n                           => clsact_chain_head_change()\n                             => mini_qdisc_pair_swap() // UAF\n\nThere are also other variants, the gist is to add an ingress (or clsact)\nqdisc with a specific shared block, then to replace that qdisc, waiting\nfor the tcx_entry kfree_rcu() to be executed and subsequently accessing\nthe current active qdisc's miniq one way or another.\n\nThe correct fix is to turn the miniq_active boolean into a counter. What\ncan be observed, at step 2 above, the counter transitions from 0->1, at\nstep [a] from 1->2 (in order for the miniq object to remain active during\nthe replacement), then in [b] from 2->1 and finally [c] 1->0 with the\neventual release. The reference counter in general ranges from [0,2] and\nit does not need to be atomic since all access to the counter is protected\nby the rtnl mutex. With this in place, there is no longer a UAF happening\nand the tcx_entry is freed at the correct time.","published":"2024-07-17T07:15:02.000Z","lastModified":"2026-08-04T11:19:16.000Z","status":"Modified","sourceIdentifier":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","cvss":{"version":"3.1","score":5.5,"severity":"MEDIUM","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"},"cwe":["CWE-416"],"affected":["linux/linux kernel"],"epss":{"score":0.00367,"percentile":0.30325,"date":"2026-10-26","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"low","text":"Lower severity and a low EPSS score (0.37%). Track it; it rarely justifies an emergency change on its own."},"changes":[],"references":[{"url":"https://git.kernel.org/stable/c/1cb6f0bae50441f4b4b32a28315853b279c7404e","tags":["Mailing List","Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/230bb13650b0f186f540500fd5f5f7096a822a2a","tags":["Mailing List","Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/f61ecf1bd5b562ebfd7d430ccb31619857e80857","tags":["Mailing List","Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/1cb6f0bae50441f4b4b32a28315853b279c7404e","tags":["Mailing List","Patch"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://git.kernel.org/stable/c/230bb13650b0f186f540500fd5f5f7096a822a2a","tags":["Mailing List","Patch"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://git.kernel.org/stable/c/f61ecf1bd5b562ebfd7d430ccb31619857e80857","tags":["Mailing List","Patch"],"source":"af854a3a-2127-422b-91ae-364da2661108"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2024-41010","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}