248 lines
15 KiB
JSON
248 lines
15 KiB
JSON
{
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"dataType": "CVE_RECORD",
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"dataVersion": "5.2",
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"cveMetadata": {
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"cveId": "CVE-2021-47402",
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"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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"state": "PUBLISHED",
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"assignerShortName": "Linux",
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"dateReserved": "2024-05-21T14:58:30.816Z",
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"datePublished": "2024-05-21T15:03:56.690Z",
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"dateUpdated": "2026-08-05T08:47:42.173Z"
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},
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"containers": {
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"cna": {
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"providerMetadata": {
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"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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"shortName": "Linux",
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"dateUpdated": "2026-08-05T08:47:42.173Z"
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},
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"descriptions": [
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{
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"lang": "en",
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: sched: flower: protect fl_walk() with rcu\n\nPatch that refactored fl_walk() to use idr_for_each_entry_continue_ul()\nalso removed rcu protection of individual filters which causes following\nuse-after-free when filter is deleted concurrently. Fix fl_walk() to obtain\nrcu read lock while iterating and taking the filter reference and temporary\nrelease the lock while calling arg->fn() callback that can sleep.\n\nKASAN trace:\n\n[ 352.773640] ==================================================================\n[ 352.775041] BUG: KASAN: use-after-free in fl_walk+0x159/0x240 [cls_flower]\n[ 352.776304] Read of size 4 at addr ffff8881c8251480 by task tc/2987\n\n[ 352.777862] CPU: 3 PID: 2987 Comm: tc Not tainted 5.15.0-rc2+ #2\n[ 352.778980] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014\n[ 352.781022] Call Trace:\n[ 352.781573] dump_stack_lvl+0x46/0x5a\n[ 352.782332] print_address_description.constprop.0+0x1f/0x140\n[ 352.783400] ? fl_walk+0x159/0x240 [cls_flower]\n[ 352.784292] ? fl_walk+0x159/0x240 [cls_flower]\n[ 352.785138] kasan_report.cold+0x83/0xdf\n[ 352.785851] ? fl_walk+0x159/0x240 [cls_flower]\n[ 352.786587] kasan_check_range+0x145/0x1a0\n[ 352.787337] fl_walk+0x159/0x240 [cls_flower]\n[ 352.788163] ? fl_put+0x10/0x10 [cls_flower]\n[ 352.789007] ? __mutex_unlock_slowpath.constprop.0+0x220/0x220\n[ 352.790102] tcf_chain_dump+0x231/0x450\n[ 352.790878] ? tcf_chain_tp_delete_empty+0x170/0x170\n[ 352.791833] ? __might_sleep+0x2e/0xc0\n[ 352.792594] ? tfilter_notify+0x170/0x170\n[ 352.793400] ? __mutex_unlock_slowpath.constprop.0+0x220/0x220\n[ 352.794477] tc_dump_tfilter+0x385/0x4b0\n[ 352.795262] ? tc_new_tfilter+0x1180/0x1180\n[ 352.796103] ? __mod_node_page_state+0x1f/0xc0\n[ 352.796974] ? __build_skb_around+0x10e/0x130\n[ 352.797826] netlink_dump+0x2c0/0x560\n[ 352.798563] ? netlink_getsockopt+0x430/0x430\n[ 352.799433] ? __mutex_unlock_slowpath.constprop.0+0x220/0x220\n[ 352.800542] __netlink_dump_start+0x356/0x440\n[ 352.801397] rtnetlink_rcv_msg+0x3ff/0x550\n[ 352.802190] ? tc_new_tfilter+0x1180/0x1180\n[ 352.802872] ? rtnl_calcit.isra.0+0x1f0/0x1f0\n[ 352.803668] ? tc_new_tfilter+0x1180/0x1180\n[ 352.804344] ? _copy_from_iter_nocache+0x800/0x800\n[ 352.805202] ? kasan_set_track+0x1c/0x30\n[ 352.805900] netlink_rcv_skb+0xc6/0x1f0\n[ 352.806587] ? rht_deferred_worker+0x6b0/0x6b0\n[ 352.807455] ? rtnl_calcit.isra.0+0x1f0/0x1f0\n[ 352.808324] ? netlink_ack+0x4d0/0x4d0\n[ 352.809086] ? netlink_deliver_tap+0x62/0x3d0\n[ 352.809951] netlink_unicast+0x353/0x480\n[ 352.810744] ? netlink_attachskb+0x430/0x430\n[ 352.811586] ? __alloc_skb+0xd7/0x200\n[ 352.812349] netlink_sendmsg+0x396/0x680\n[ 352.813132] ? netlink_unicast+0x480/0x480\n[ 352.813952] ? __import_iovec+0x192/0x210\n[ 352.814759] ? netlink_unicast+0x480/0x480\n[ 352.815580] sock_sendmsg+0x6c/0x80\n[ 352.816299] ____sys_sendmsg+0x3a5/0x3c0\n[ 352.817096] ? kernel_sendmsg+0x30/0x30\n[ 352.817873] ? __ia32_sys_recvmmsg+0x150/0x150\n[ 352.818753] ___sys_sendmsg+0xd8/0x140\n[ 352.819518] ? sendmsg_copy_msghdr+0x110/0x110\n[ 352.820402] ? ___sys_recvmsg+0xf4/0x1a0\n[ 352.821110] ? __copy_msghdr_from_user+0x260/0x260\n[ 352.821934] ? _raw_spin_lock+0x81/0xd0\n[ 352.822680] ? __handle_mm_fault+0xef3/0x1b20\n[ 352.823549] ? rb_insert_color+0x2a/0x270\n[ 352.824373] ? copy_page_range+0x16b0/0x16b0\n[ 352.825209] ? perf_event_update_userpage+0x2d0/0x2d0\n[ 352.826190] ? __fget_light+0xd9/0xf0\n[ 352.826941] __sys_sendmsg+0xb3/0x130\n[ 352.827613] ? __sys_sendmsg_sock+0x20/0x20\n[ 352.828377] ? do_user_addr_fault+0x2c5/0x8a0\n[ 352.829184] ? fpregs_assert_state_consistent+0x52/0x60\n[ 352.830001] ? exit_to_user_mode_prepare+0x32/0x160\n[ 352.830845] do_syscall_64+0x35/0x80\n[ 352.831445] entry_SYSCALL_64_after_hwframe+0x44/0xae\n[ 352.832331] RIP: 0033:0x7f7bee973c17\n[ \n---truncated---"
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}
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],
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"metrics": [
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{
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"cvssV3_1": {
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"version": "3.1",
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"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
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"baseScore": 7.8,
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"baseSeverity": "HIGH"
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},
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"scenarios": [
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{
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"lang": "en",
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"value": "AV:L - The bug is triggered through local rtnetlink/tc syscalls (sendmsg → rtnetlink_rcv_msg → tc_dump_tfilter/tc_del_tfilter → fl_walk), not via remotely processed packets.\nAC:L - The attacker controls both sides of the race by concurrently dumping and deleting flower filters they created; flower is TCF_PROTO_OPS_DOIT_UNLOCKED so dump and delete can run without full rtnl serialization.\nPR:L - Creating/deleting filters requires CAP_NET_ADMIN via netlink_net_capable, which an unprivileged user obtains in a user+net namespace (unshare -Urn); tc/qdisc in userns is PR:L per guidance.\nUI:N - Exploitation requires only the attacker’s own netlink operations; no victim action is needed.\nS:U - Impact is confined to the local kernel privilege boundary (standard local privilege escalation/DoS); it does not cross VM, IOMMU, or other security authorities.\nC:H - This is a use-after-free of a kmalloc-2k cls_fl_filter; UAF enables reclaim/spray of the freed object and arbitrary read primitives, including via the dump callback path.\nI:H - UAF of the filter object enables heap spraying and write/control-flow hijacking primitives once the freed slot is reclaimed with attacker-controlled data.\nA:H - The UAF produces a kernel oops/KASAN use-after-free (confirmed in the fix commit trace) and can crash or hang the system even without full exploitation."
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}
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} |