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CVE-2021-47103 (GCVE-0-2021-47103)

Vulnerability from cvelistv5 – Published: 2024-03-04 18:10 – Updated: 2026-08-05 08:46
VLAI
Title
inet: fully convert sk->sk_rx_dst to RCU rules
Summary
In the Linux kernel, the following vulnerability has been resolved: inet: fully convert sk->sk_rx_dst to RCU rules syzbot reported various issues around early demux, one being included in this changelog [1] sk->sk_rx_dst is using RCU protection without clearly documenting it. And following sequences in tcp_v4_do_rcv()/tcp_v6_do_rcv() are not following standard RCU rules. [a] dst_release(dst); [b] sk->sk_rx_dst = NULL; They look wrong because a delete operation of RCU protected pointer is supposed to clear the pointer before the call_rcu()/synchronize_rcu() guarding actual memory freeing. In some cases indeed, dst could be freed before [b] is done. We could cheat by clearing sk_rx_dst before calling dst_release(), but this seems the right time to stick to standard RCU annotations and debugging facilities. [1] BUG: KASAN: use-after-free in dst_check include/net/dst.h:470 [inline] BUG: KASAN: use-after-free in tcp_v4_early_demux+0x95b/0x960 net/ipv4/tcp_ipv4.c:1792 Read of size 2 at addr ffff88807f1cb73a by task syz-executor.5/9204 CPU: 0 PID: 9204 Comm: syz-executor.5 Not tainted 5.16.0-rc5-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106 print_address_description.constprop.0.cold+0x8d/0x320 mm/kasan/report.c:247 __kasan_report mm/kasan/report.c:433 [inline] kasan_report.cold+0x83/0xdf mm/kasan/report.c:450 dst_check include/net/dst.h:470 [inline] tcp_v4_early_demux+0x95b/0x960 net/ipv4/tcp_ipv4.c:1792 ip_rcv_finish_core.constprop.0+0x15de/0x1e80 net/ipv4/ip_input.c:340 ip_list_rcv_finish.constprop.0+0x1b2/0x6e0 net/ipv4/ip_input.c:583 ip_sublist_rcv net/ipv4/ip_input.c:609 [inline] ip_list_rcv+0x34e/0x490 net/ipv4/ip_input.c:644 __netif_receive_skb_list_ptype net/core/dev.c:5508 [inline] __netif_receive_skb_list_core+0x549/0x8e0 net/core/dev.c:5556 __netif_receive_skb_list net/core/dev.c:5608 [inline] netif_receive_skb_list_internal+0x75e/0xd80 net/core/dev.c:5699 gro_normal_list net/core/dev.c:5853 [inline] gro_normal_list net/core/dev.c:5849 [inline] napi_complete_done+0x1f1/0x880 net/core/dev.c:6590 virtqueue_napi_complete drivers/net/virtio_net.c:339 [inline] virtnet_poll+0xca2/0x11b0 drivers/net/virtio_net.c:1557 __napi_poll+0xaf/0x440 net/core/dev.c:7023 napi_poll net/core/dev.c:7090 [inline] net_rx_action+0x801/0xb40 net/core/dev.c:7177 __do_softirq+0x29b/0x9c2 kernel/softirq.c:558 invoke_softirq kernel/softirq.c:432 [inline] __irq_exit_rcu+0x123/0x180 kernel/softirq.c:637 irq_exit_rcu+0x5/0x20 kernel/softirq.c:649 common_interrupt+0x52/0xc0 arch/x86/kernel/irq.c:240 asm_common_interrupt+0x1e/0x40 arch/x86/include/asm/idtentry.h:629 RIP: 0033:0x7f5e972bfd57 Code: 39 d1 73 14 0f 1f 80 00 00 00 00 48 8b 50 f8 48 83 e8 08 48 39 ca 77 f3 48 39 c3 73 3e 48 89 13 48 8b 50 f8 48 89 38 49 8b 0e <48> 8b 3e 48 83 c3 08 48 83 c6 08 eb bc 48 39 d1 72 9e 48 39 d0 73 RSP: 002b:00007fff8a413210 EFLAGS: 00000283 RAX: 00007f5e97108990 RBX: 00007f5e97108338 RCX: ffffffff81d3aa45 RDX: ffffffff81d3aa45 RSI: 00007f5e97108340 RDI: ffffffff81d3aa45 RBP: 00007f5e97107eb8 R08: 00007f5e97108d88 R09: 0000000093c2e8d9 R10: 0000000000000000 R11: 0000000000000000 R12: 00007f5e97107eb0 R13: 00007f5e97108338 R14: 00007f5e97107ea8 R15: 0000000000000019 </TASK> Allocated by task 13: kasan_save_stack+0x1e/0x50 mm/kasan/common.c:38 kasan_set_track mm/kasan/common.c:46 [inline] set_alloc_info mm/kasan/common.c:434 [inline] __kasan_slab_alloc+0x90/0xc0 mm/kasan/common.c:467 kasan_slab_alloc include/linux/kasan.h:259 [inline] slab_post_alloc_hook mm/slab.h:519 [inline] slab_alloc_node mm/slub.c:3234 [inline] slab_alloc mm/slub.c:3242 [inline] kmem_cache_alloc+0x202/0x3a0 mm/slub.c:3247 dst_alloc+0x146/0x1f0 net/core/dst.c:92 rt_dst_alloc+0x73/0x430 net/ipv4/route.c:1613 ip_route_input_slow+0x1817/0x3a20 net/ipv4/route.c:234 ---truncated---
Severity
9.8 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2024-08-08 15:23 UTC
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 41063e9dd11956f2d285e12e4342e1d232ba0ea2 , < 68c34ce11ef23328692aa35fa6aaafdd75913100 (git)
Affected: 41063e9dd11956f2d285e12e4342e1d232ba0ea2 , < 92e6e36ecd16808866ac6172b9491b5097cde449 (git)
Affected: 41063e9dd11956f2d285e12e4342e1d232ba0ea2 , < 75a578000ae5e511e5d0e8433c94a14d9c99c412 (git)
Affected: 41063e9dd11956f2d285e12e4342e1d232ba0ea2 , < c3bb4a7e8cbc984e1cdac0fe6af60e880214ed6e (git)
Affected: 41063e9dd11956f2d285e12e4342e1d232ba0ea2 , < f039b43cbaea5e0700980c2f0052da05a70782e0 (git)
Affected: 41063e9dd11956f2d285e12e4342e1d232ba0ea2 , < 0249a4b8a554f2eb6a27b62516fa50168584faa4 (git)
Affected: 41063e9dd11956f2d285e12e4342e1d232ba0ea2 , < 8f905c0e7354ef261360fb7535ea079b1082c105 (git)
guessed Create a notification for this product.
Linux Linux Affected: 3.6
Unaffected: 0 , < 3.6 (semver)
Unaffected: 4.9.331 , ≤ 4.9.* (semver)
Unaffected: 4.14.296 , ≤ 4.14.* (semver)
Unaffected: 4.19.262 , ≤ 4.19.* (semver)
Unaffected: 5.4.220 , ≤ 5.4.* (semver)
Unaffected: 5.10.150 , ≤ 5.10.* (semver)
Unaffected: 5.15.12 , ≤ 5.15.* (semver)
Unaffected: 5.16 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ninet: fully convert sk-\u003esk_rx_dst to RCU rules\n\nsyzbot reported various issues around early demux,\none being included in this changelog [1]\n\nsk-\u003esk_rx_dst is using RCU protection without clearly\ndocumenting it.\n\nAnd following sequences in tcp_v4_do_rcv()/tcp_v6_do_rcv()\nare not following standard RCU rules.\n\n[a]    dst_release(dst);\n[b]    sk-\u003esk_rx_dst = NULL;\n\nThey look wrong because a delete operation of RCU protected\npointer is supposed to clear the pointer before\nthe call_rcu()/synchronize_rcu() guarding actual memory freeing.\n\nIn some cases indeed, dst could be freed before [b] is done.\n\nWe could cheat by clearing sk_rx_dst before calling\ndst_release(), but this seems the right time to stick\nto standard RCU annotations and debugging facilities.\n\n[1]\nBUG: KASAN: use-after-free in dst_check include/net/dst.h:470 [inline]\nBUG: KASAN: use-after-free in tcp_v4_early_demux+0x95b/0x960 net/ipv4/tcp_ipv4.c:1792\nRead of size 2 at addr ffff88807f1cb73a by task syz-executor.5/9204\n\nCPU: 0 PID: 9204 Comm: syz-executor.5 Not tainted 5.16.0-rc5-syzkaller #0\nHardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011\nCall Trace:\n \u003cTASK\u003e\n __dump_stack lib/dump_stack.c:88 [inline]\n dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106\n print_address_description.constprop.0.cold+0x8d/0x320 mm/kasan/report.c:247\n __kasan_report mm/kasan/report.c:433 [inline]\n kasan_report.cold+0x83/0xdf mm/kasan/report.c:450\n dst_check include/net/dst.h:470 [inline]\n tcp_v4_early_demux+0x95b/0x960 net/ipv4/tcp_ipv4.c:1792\n ip_rcv_finish_core.constprop.0+0x15de/0x1e80 net/ipv4/ip_input.c:340\n ip_list_rcv_finish.constprop.0+0x1b2/0x6e0 net/ipv4/ip_input.c:583\n ip_sublist_rcv net/ipv4/ip_input.c:609 [inline]\n ip_list_rcv+0x34e/0x490 net/ipv4/ip_input.c:644\n __netif_receive_skb_list_ptype net/core/dev.c:5508 [inline]\n __netif_receive_skb_list_core+0x549/0x8e0 net/core/dev.c:5556\n __netif_receive_skb_list net/core/dev.c:5608 [inline]\n netif_receive_skb_list_internal+0x75e/0xd80 net/core/dev.c:5699\n gro_normal_list net/core/dev.c:5853 [inline]\n gro_normal_list net/core/dev.c:5849 [inline]\n napi_complete_done+0x1f1/0x880 net/core/dev.c:6590\n virtqueue_napi_complete drivers/net/virtio_net.c:339 [inline]\n virtnet_poll+0xca2/0x11b0 drivers/net/virtio_net.c:1557\n __napi_poll+0xaf/0x440 net/core/dev.c:7023\n napi_poll net/core/dev.c:7090 [inline]\n net_rx_action+0x801/0xb40 net/core/dev.c:7177\n __do_softirq+0x29b/0x9c2 kernel/softirq.c:558\n invoke_softirq kernel/softirq.c:432 [inline]\n __irq_exit_rcu+0x123/0x180 kernel/softirq.c:637\n irq_exit_rcu+0x5/0x20 kernel/softirq.c:649\n common_interrupt+0x52/0xc0 arch/x86/kernel/irq.c:240\n asm_common_interrupt+0x1e/0x40 arch/x86/include/asm/idtentry.h:629\nRIP: 0033:0x7f5e972bfd57\nCode: 39 d1 73 14 0f 1f 80 00 00 00 00 48 8b 50 f8 48 83 e8 08 48 39 ca 77 f3 48 39 c3 73 3e 48 89 13 48 8b 50 f8 48 89 38 49 8b 0e \u003c48\u003e 8b 3e 48 83 c3 08 48 83 c6 08 eb bc 48 39 d1 72 9e 48 39 d0 73\nRSP: 002b:00007fff8a413210 EFLAGS: 00000283\nRAX: 00007f5e97108990 RBX: 00007f5e97108338 RCX: ffffffff81d3aa45\nRDX: ffffffff81d3aa45 RSI: 00007f5e97108340 RDI: ffffffff81d3aa45\nRBP: 00007f5e97107eb8 R08: 00007f5e97108d88 R09: 0000000093c2e8d9\nR10: 0000000000000000 R11: 0000000000000000 R12: 00007f5e97107eb0\nR13: 00007f5e97108338 R14: 00007f5e97107ea8 R15: 0000000000000019\n \u003c/TASK\u003e\n\nAllocated by task 13:\n kasan_save_stack+0x1e/0x50 mm/kasan/common.c:38\n kasan_set_track mm/kasan/common.c:46 [inline]\n set_alloc_info mm/kasan/common.c:434 [inline]\n __kasan_slab_alloc+0x90/0xc0 mm/kasan/common.c:467\n kasan_slab_alloc include/linux/kasan.h:259 [inline]\n slab_post_alloc_hook mm/slab.h:519 [inline]\n slab_alloc_node mm/slub.c:3234 [inline]\n slab_alloc mm/slub.c:3242 [inline]\n kmem_cache_alloc+0x202/0x3a0 mm/slub.c:3247\n dst_alloc+0x146/0x1f0 net/core/dst.c:92\n rt_dst_alloc+0x73/0x430 net/ipv4/route.c:1613\n ip_route_input_slow+0x1817/0x3a20 net/ipv4/route.c:234\n---truncated---"
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              "value": "AV:N - The UAF is hit in tcp_v4_early_demux/udp early_demux and the buggy dst_release runs in tcp_v4_do_rcv while processing received packets on established sockets\u2014the default-on inet early-demux path on internet-facing TCP/UDP services.\nAC:L - A remote peer controls both sides: ICMP FRAG_NEEDED drives PMTU updates that mark the cached RX dst obsolete (DST_OBSOLETE_KILL), then a packet burst races do_rcv\u2019s dst_release-before-NULL against concurrent early_demux reads.\nPR:N - No host account or capability is required; any unauthenticated network peer of an open TCP/UDP service can complete a handshake and send the packets/ICMP that reach the vulnerable softirq paths.\nUI:N - Exploitation needs only attacker-sent packets to a listening service; no local user action such as mounting, opening a file, or clicking is required.\nS:U - Impact is kernel heap UAF within the host\u2019s networking authority and does not cross a VM, IOMMU, or other security boundary.\nC:H - This is a confirmed use-after-free of a slab-allocated dst_entry (ip_dst_cache); freed dst memory can be sprayed and re-read via dst_check/early demux, enabling arbitrary kernel disclosure.\nI:H - The same dst_entry UAF is heap-corruptible and, once reclaimed under attacker control, yields write/control-flow primitives through subsequent dst ops and noref skb_dst use.\nA:H - KASAN already showed a kernel use-after-free oops in dst_check during softirq receive; the crash is repeatable and fully denies host availability."
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    "datePublished": "2024-03-04T18:10:57.116Z",
    "dateReserved": "2024-02-29T22:33:44.301Z",
    "dateUpdated": "2026-08-05T08:46:00.322Z",
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          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ninet: fully convert sk-\u003esk_rx_dst to RCU rules\n\nsyzbot reported various issues around early demux,\none being included in this changelog [1]\n\nsk-\u003esk_rx_dst is using RCU protection without clearly\ndocumenting it.\n\nAnd following sequences in tcp_v4_do_rcv()/tcp_v6_do_rcv()\nare not following standard RCU rules.\n\n[a]    dst_release(dst);\n[b]    sk-\u003esk_rx_dst = NULL;\n\nThey look wrong because a delete operation of RCU protected\npointer is supposed to clear the pointer before\nthe call_rcu()/synchronize_rcu() guarding actual memory freeing.\n\nIn some cases indeed, dst could be freed before [b] is done.\n\nWe could cheat by clearing sk_rx_dst before calling\ndst_release(), but this seems the right time to stick\nto standard RCU annotations and debugging facilities.\n\n[1]\nBUG: KASAN: use-after-free in dst_check include/net/dst.h:470 [inline]\nBUG: KASAN: use-after-free in tcp_v4_early_demux+0x95b/0x960 net/ipv4/tcp_ipv4.c:1792\nRead of size 2 at addr ffff88807f1cb73a by task syz-executor.5/9204\n\nCPU: 0 PID: 9204 Comm: syz-executor.5 Not tainted 5.16.0-rc5-syzkaller #0\nHardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011\nCall Trace:\n \u003cTASK\u003e\n __dump_stack lib/dump_stack.c:88 [inline]\n dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106\n print_address_description.constprop.0.cold+0x8d/0x320 mm/kasan/report.c:247\n __kasan_report mm/kasan/report.c:433 [inline]\n kasan_report.cold+0x83/0xdf mm/kasan/report.c:450\n dst_check include/net/dst.h:470 [inline]\n tcp_v4_early_demux+0x95b/0x960 net/ipv4/tcp_ipv4.c:1792\n ip_rcv_finish_core.constprop.0+0x15de/0x1e80 net/ipv4/ip_input.c:340\n ip_list_rcv_finish.constprop.0+0x1b2/0x6e0 net/ipv4/ip_input.c:583\n ip_sublist_rcv net/ipv4/ip_input.c:609 [inline]\n ip_list_rcv+0x34e/0x490 net/ipv4/ip_input.c:644\n __netif_receive_skb_list_ptype net/core/dev.c:5508 [inline]\n __netif_receive_skb_list_core+0x549/0x8e0 net/core/dev.c:5556\n __netif_receive_skb_list net/core/dev.c:5608 [inline]\n netif_receive_skb_list_internal+0x75e/0xd80 net/core/dev.c:5699\n gro_normal_list net/core/dev.c:5853 [inline]\n gro_normal_list net/core/dev.c:5849 [inline]\n napi_complete_done+0x1f1/0x880 net/core/dev.c:6590\n virtqueue_napi_complete drivers/net/virtio_net.c:339 [inline]\n virtnet_poll+0xca2/0x11b0 drivers/net/virtio_net.c:1557\n __napi_poll+0xaf/0x440 net/core/dev.c:7023\n napi_poll net/core/dev.c:7090 [inline]\n net_rx_action+0x801/0xb40 net/core/dev.c:7177\n __do_softirq+0x29b/0x9c2 kernel/softirq.c:558\n invoke_softirq kernel/softirq.c:432 [inline]\n __irq_exit_rcu+0x123/0x180 kernel/softirq.c:637\n irq_exit_rcu+0x5/0x20 kernel/softirq.c:649\n common_interrupt+0x52/0xc0 arch/x86/kernel/irq.c:240\n asm_common_interrupt+0x1e/0x40 arch/x86/include/asm/idtentry.h:629\nRIP: 0033:0x7f5e972bfd57\nCode: 39 d1 73 14 0f 1f 80 00 00 00 00 48 8b 50 f8 48 83 e8 08 48 39 ca 77 f3 48 39 c3 73 3e 48 89 13 48 8b 50 f8 48 89 38 49 8b 0e \u003c48\u003e 8b 3e 48 83 c3 08 48 83 c6 08 eb bc 48 39 d1 72 9e 48 39 d0 73\nRSP: 002b:00007fff8a413210 EFLAGS: 00000283\nRAX: 00007f5e97108990 RBX: 00007f5e97108338 RCX: ffffffff81d3aa45\nRDX: ffffffff81d3aa45 RSI: 00007f5e97108340 RDI: ffffffff81d3aa45\nRBP: 00007f5e97107eb8 R08: 00007f5e97108d88 R09: 0000000093c2e8d9\nR10: 0000000000000000 R11: 0000000000000000 R12: 00007f5e97107eb0\nR13: 00007f5e97108338 R14: 00007f5e97107ea8 R15: 0000000000000019\n \u003c/TASK\u003e\n\nAllocated by task 13:\n kasan_save_stack+0x1e/0x50 mm/kasan/common.c:38\n kasan_set_track mm/kasan/common.c:46 [inline]\n set_alloc_info mm/kasan/common.c:434 [inline]\n __kasan_slab_alloc+0x90/0xc0 mm/kasan/common.c:467\n kasan_slab_alloc include/linux/kasan.h:259 [inline]\n slab_post_alloc_hook mm/slab.h:519 [inline]\n slab_alloc_node mm/slub.c:3234 [inline]\n slab_alloc mm/slub.c:3242 [inline]\n kmem_cache_alloc+0x202/0x3a0 mm/slub.c:3247\n dst_alloc+0x146/0x1f0 net/core/dst.c:92\n rt_dst_alloc+0x73/0x430 net/ipv4/route.c:1613\n ip_route_input_slow+0x1817/0x3a20 net/ipv4/route.c:234\n---truncated---"
          },
          {
            "lang": "es",
            "value": "En el kernel de Linux, se resolvi\u00f3 la siguiente vulnerabilidad: inet: conversi\u00f3n completa de sk-\u0026gt;sk_rx_dst a reglas de RCU syzbot inform\u00f3 varios problemas relacionados con la demux inicial, uno de los cuales se incluye en este registro de cambios [1] sk-\u0026gt;sk_rx_dst est\u00e1 usando protecci\u00f3n de RCU sin claridad document\u00e1ndolo. Y las siguientes secuencias en tcp_v4_do_rcv()/tcp_v6_do_rcv() no siguen las reglas est\u00e1ndar de RCU. [a] dst_release(dst); [b] sk-\u0026gt;sk_rx_dst = NULL; Se ven incorrectos porque se supone que una operaci\u00f3n de eliminaci\u00f3n del puntero protegido de RCU borra el puntero antes de que call_rcu()/synchronize_rcu() proteja la liberaci\u00f3n de memoria real. De hecho, en algunos casos, dst podr\u00eda liberarse antes de que se realice [b]. Podr\u00edamos hacer trampa borrando sk_rx_dst antes de llamar a dst_release(), pero este parece el momento adecuado para ce\u00f1irnos a las anotaciones est\u00e1ndar de RCU y las funciones de depuraci\u00f3n.  [1] BUG: KASAN: use-after-free in dst_check include/net/dst.h:470 [inline] BUG: KASAN: use-after-free in tcp_v4_early_demux+0x95b/0x960 net/ipv4/tcp_ipv4.c:1792 Read of size 2 at addr ffff88807f1cb73a by task syz-executor.5/9204 CPU: 0 PID: 9204 Comm: syz-executor.5 Not tainted 5.16.0-rc5-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace:  __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106 print_address_description.constprop.0.cold+0x8d/0x320 mm/kasan/report.c:247 __kasan_report mm/kasan/report.c:433 [inline] kasan_report.cold+0x83/0xdf mm/kasan/report.c:450 dst_check include/net/dst.h:470 [inline] tcp_v4_early_demux+0x95b/0x960 net/ipv4/tcp_ipv4.c:1792 ip_rcv_finish_core.constprop.0+0x15de/0x1e80 net/ipv4/ip_input.c:340 ip_list_rcv_finish.constprop.0+0x1b2/0x6e0 net/ipv4/ip_input.c:583 ip_sublist_rcv net/ipv4/ip_input.c:609 [inline] ip_list_rcv+0x34e/0x490 net/ipv4/ip_input.c:644 __netif_receive_skb_list_ptype net/core/dev.c:5508 [inline] __netif_receive_skb_list_core+0x549/0x8e0 net/core/dev.c:5556 __netif_receive_skb_list net/core/dev.c:5608 [inline] netif_receive_skb_list_internal+0x75e/0xd80 net/core/dev.c:5699 gro_normal_list net/core/dev.c:5853 [inline] gro_normal_list net/core/dev.c:5849 [inline] napi_complete_done+0x1f1/0x880 net/core/dev.c:6590 virtqueue_napi_complete drivers/net/virtio_net.c:339 [inline] virtnet_poll+0xca2/0x11b0 drivers/net/virtio_net.c:1557 __napi_poll+0xaf/0x440 net/core/dev.c:7023 napi_poll net/core/dev.c:7090 [inline] net_rx_action+0x801/0xb40 net/core/dev.c:7177 __do_softirq+0x29b/0x9c2 kernel/softirq.c:558 invoke_softirq kernel/softirq.c:432 [inline] __irq_exit_rcu+0x123/0x180 kernel/softirq.c:637 irq_exit_rcu+0x5/0x20 kernel/softirq.c:649 common_interrupt+0x52/0xc0 arch/x86/kernel/irq.c:240 asm_common_interrupt+0x1e/0x40 arch/x86/include/asm/idtentry.h:629 RIP: 0033:0x7f5e972bfd57 Code: 39 d1 73 14 0f 1f 80 00 00 00 00 48 8b 50 f8 48 83 e8 08 48 39 ca 77 f3 48 39 c3 73 3e 48 89 13 48 8b 50 f8 48 89 38 49 8b 0e \u0026lt;48\u0026gt; 8b 3e 48 83 c3 08 48 83 c6 08 eb bc 48 39 d1 72 9e 48 39 d0 73 RSP: 002b:00007fff8a413210 EFLAGS: 00000283 RAX: 00007f5e97108990 RBX: 00007f5e97108338 RCX: ffffffff81d3aa45 RDX: ffffffff81d3aa45 RSI: 00007f5e97108340 RDI: ffffffff81d3aa45 RBP: 00007f5e97107eb8 R08: 00007f5e97108d88 R09: 0000000093c2e8d9 R10: 0000000000000000 R11: 0000000000000000 R12: 00007f5e97107eb0 R13: 00007f5e97108338 R14: 00007f5e97107ea8 R15: 0000000000000019  Allocated by task 13: kasan_save_stack+0x1e/0x50 mm/kasan/common.c:38 kasan_set_track mm/kasan/common.c:46 [inline] set_alloc_info mm/kasan/common.c:434 [inline] __kasan_slab_alloc+0x90/0xc0 mm/kasan/common.c:467 kasan_slab_alloc include/linux/kasan.h:259 [inline] slab_post_alloc_hook mm/slab.h:519 [inline] slab_alloc_node mm/slub.c:3234 [inline] slab_alloc mm/slub.c:3242 [inline] kmem_cache_alloc+0x202/0x3a0 mm/slub.c:3247 dst_alloc+0x146/0x1f0 net/core/dst.c:92 rt_dst_alloc+0x73/0x430 net/ipv4/route.c:1613 ip_route_input_slow+0x1817/0x3a20 net/ipv4/route.c:234"
          }
        ],
        "id": "CVE-2021-47103",
        "lastModified": "2026-08-04T10:16:45.763",
        "metrics": {
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                "attackVector": "NETWORK",
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                "baseScore": 9.8,
                "baseSeverity": "CRITICAL",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "NONE",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
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              "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
              "type": "Secondary"
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                "baseScore": 7.8,
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                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
                "version": "3.1"
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              "source": "nvd@nist.gov",
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          "ssvcV203": [
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                  },
                  {
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                  {
                    "technicalImpact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2024-08-08T15:23:27.864349Z",
                "version": "2.0.3"
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        },
        "published": "2024-03-04T18:15:08.667",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
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              "Mailing List",
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              "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ninet: fully convert sk-\u003esk_rx_dst to RCU rules\n\nsyzbot reported various issues around early demux,\none being included in this changelog [1]\n\nsk-\u003esk_rx_dst is using RCU protection without clearly\ndocumenting it.\n\nAnd following sequences in tcp_v4_do_rcv()/tcp_v6_do_rcv()\nare not following standard RCU rules.\n\n[a]    dst_release(dst);\n[b]    sk-\u003esk_rx_dst = NULL;\n\nThey look wrong because a delete operation of RCU protected\npointer is supposed to clear the pointer before\nthe call_rcu()/synchronize_rcu() guarding actual memory freeing.\n\nIn some cases indeed, dst could be freed before [b] is done.\n\nWe could cheat by clearing sk_rx_dst before calling\ndst_release(), but this seems the right time to stick\nto standard RCU annotations and debugging facilities.\n\n[1]\nBUG: KASAN: use-after-free in dst_check include/net/dst.h:470 [inline]\nBUG: KASAN: use-after-free in tcp_v4_early_demux+0x95b/0x960 net/ipv4/tcp_ipv4.c:1792\nRead of size 2 at addr ffff88807f1cb73a by task syz-executor.5/9204\n\nCPU: 0 PID: 9204 Comm: syz-executor.5 Not tainted 5.16.0-rc5-syzkaller #0\nHardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011\nCall Trace:\n \u003cTASK\u003e\n __dump_stack lib/dump_stack.c:88 [inline]\n dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106\n print_address_description.constprop.0.cold+0x8d/0x320 mm/kasan/report.c:247\n __kasan_report mm/kasan/report.c:433 [inline]\n kasan_report.cold+0x83/0xdf mm/kasan/report.c:450\n dst_check include/net/dst.h:470 [inline]\n tcp_v4_early_demux+0x95b/0x960 net/ipv4/tcp_ipv4.c:1792\n ip_rcv_finish_core.constprop.0+0x15de/0x1e80 net/ipv4/ip_input.c:340\n ip_list_rcv_finish.constprop.0+0x1b2/0x6e0 net/ipv4/ip_input.c:583\n ip_sublist_rcv net/ipv4/ip_input.c:609 [inline]\n ip_list_rcv+0x34e/0x490 net/ipv4/ip_input.c:644\n __netif_receive_skb_list_ptype net/core/dev.c:5508 [inline]\n __netif_receive_skb_list_core+0x549/0x8e0 net/core/dev.c:5556\n __netif_receive_skb_list net/core/dev.c:5608 [inline]\n netif_receive_skb_list_internal+0x75e/0xd80 net/core/dev.c:5699\n gro_normal_list net/core/dev.c:5853 [inline]\n gro_normal_list net/core/dev.c:5849 [inline]\n napi_complete_done+0x1f1/0x880 net/core/dev.c:6590\n virtqueue_napi_complete drivers/net/virtio_net.c:339 [inline]\n virtnet_poll+0xca2/0x11b0 drivers/net/virtio_net.c:1557\n __napi_poll+0xaf/0x440 net/core/dev.c:7023\n napi_poll net/core/dev.c:7090 [inline]\n net_rx_action+0x801/0xb40 net/core/dev.c:7177\n __do_softirq+0x29b/0x9c2 kernel/softirq.c:558\n invoke_softirq kernel/softirq.c:432 [inline]\n __irq_exit_rcu+0x123/0x180 kernel/softirq.c:637\n irq_exit_rcu+0x5/0x20 kernel/softirq.c:649\n common_interrupt+0x52/0xc0 arch/x86/kernel/irq.c:240\n asm_common_interrupt+0x1e/0x40 arch/x86/include/asm/idtentry.h:629\nRIP: 0033:0x7f5e972bfd57\nCode: 39 d1 73 14 0f 1f 80 00 00 00 00 48 8b 50 f8 48 83 e8 08 48 39 ca 77 f3 48 39 c3 73 3e 48 89 13 48 8b 50 f8 48 89 38 49 8b 0e \u003c48\u003e 8b 3e 48 83 c3 08 48 83 c6 08 eb bc 48 39 d1 72 9e 48 39 d0 73\nRSP: 002b:00007fff8a413210 EFLAGS: 00000283\nRAX: 00007f5e97108990 RBX: 00007f5e97108338 RCX: ffffffff81d3aa45\nRDX: ffffffff81d3aa45 RSI: 00007f5e97108340 RDI: ffffffff81d3aa45\nRBP: 00007f5e97107eb8 R08: 00007f5e97108d88 R09: 0000000093c2e8d9\nR10: 0000000000000000 R11: 0000000000000000 R12: 00007f5e97107eb0\nR13: 00007f5e97108338 R14: 00007f5e97107ea8 R15: 0000000000000019\n \u003c/TASK\u003e\n\nAllocated by task 13:\n kasan_save_stack+0x1e/0x50 mm/kasan/common.c:38\n kasan_set_track mm/kasan/common.c:46 [inline]\n set_alloc_info mm/kasan/common.c:434 [inline]\n __kasan_slab_alloc+0x90/0xc0 mm/kasan/common.c:467\n kasan_slab_alloc include/linux/kasan.h:259 [inline]\n slab_post_alloc_hook mm/slab.h:519 [inline]\n slab_alloc_node mm/slub.c:3234 [inline]\n slab_alloc mm/slub.c:3242 [inline]\n kmem_cache_alloc+0x202/0x3a0 mm/slub.c:3247\n dst_alloc+0x146/0x1f0 net/core/dst.c:92\n rt_dst_alloc+0x73/0x430 net/ipv4/route.c:1613\n ip_route_input_slow+0x1817/0x3a20 net/ipv4/route.c:234\n---truncated---"
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                  "value": "AV:N - The UAF is hit in tcp_v4_early_demux/udp early_demux and the buggy dst_release runs in tcp_v4_do_rcv while processing received packets on established sockets\u2014the default-on inet early-demux path on internet-facing TCP/UDP services.\nAC:L - A remote peer controls both sides: ICMP FRAG_NEEDED drives PMTU updates that mark the cached RX dst obsolete (DST_OBSOLETE_KILL), then a packet burst races do_rcv\u2019s dst_release-before-NULL against concurrent early_demux reads.\nPR:N - No host account or capability is required; any unauthenticated network peer of an open TCP/UDP service can complete a handshake and send the packets/ICMP that reach the vulnerable softirq paths.\nUI:N - Exploitation needs only attacker-sent packets to a listening service; no local user action such as mounting, opening a file, or clicking is required.\nS:U - Impact is kernel heap UAF within the host\u2019s networking authority and does not cross a VM, IOMMU, or other security boundary.\nC:H - This is a confirmed use-after-free of a slab-allocated dst_entry (ip_dst_cache); freed dst memory can be sprayed and re-read via dst_check/early demux, enabling arbitrary kernel disclosure.\nI:H - The same dst_entry UAF is heap-corruptible and, once reclaimed under attacker control, yields write/control-flow primitives through subsequent dst ops and noref skb_dst use.\nA:H - KASAN already showed a kernel use-after-free oops in dst_check during softirq receive; the crash is repeatable and fully denies host availability."
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}



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Tags
Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.


Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.