{
    "dataType": "CVE_RECORD",
    "dataVersion": "5.2",
    "cveMetadata": {
        "cveId": "CVE-2024-40954",
        "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "state": "PUBLISHED",
        "assignerShortName": "Linux",
        "dateReserved": "2024-07-12T12:17:45.592Z",
        "datePublished": "2024-07-12T12:31:57.517Z",
        "dateUpdated": "2026-08-05T11:34:13.912Z"
    },
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                "dateUpdated": "2026-08-05T11:34:13.912Z"
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                    "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: do not leave a dangling sk pointer, when socket creation fails\n\nIt is possible to trigger a use-after-free by:\n  * attaching an fentry probe to __sock_release() and the probe calling the\n    bpf_get_socket_cookie() helper\n  * running traceroute -I 1.1.1.1 on a freshly booted VM\n\nA KASAN enabled kernel will log something like below (decoded and stripped):\n==================================================================\nBUG: KASAN: slab-use-after-free in __sock_gen_cookie (./arch/x86/include/asm/atomic64_64.h:15 ./include/linux/atomic/atomic-arch-fallback.h:2583 ./include/linux/atomic/atomic-instrumented.h:1611 net/core/sock_diag.c:29)\nRead of size 8 at addr ffff888007110dd8 by task traceroute/299\n\nCPU: 2 PID: 299 Comm: traceroute Tainted: G            E      6.10.0-rc2+ #2\nHardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-debian-1.16.2-1 04/01/2014\nCall Trace:\n <TASK>\ndump_stack_lvl (lib/dump_stack.c:117 (discriminator 1))\nprint_report (mm/kasan/report.c:378 mm/kasan/report.c:488)\n? __sock_gen_cookie (./arch/x86/include/asm/atomic64_64.h:15 ./include/linux/atomic/atomic-arch-fallback.h:2583 ./include/linux/atomic/atomic-instrumented.h:1611 net/core/sock_diag.c:29)\nkasan_report (mm/kasan/report.c:603)\n? __sock_gen_cookie (./arch/x86/include/asm/atomic64_64.h:15 ./include/linux/atomic/atomic-arch-fallback.h:2583 ./include/linux/atomic/atomic-instrumented.h:1611 net/core/sock_diag.c:29)\nkasan_check_range (mm/kasan/generic.c:183 mm/kasan/generic.c:189)\n__sock_gen_cookie (./arch/x86/include/asm/atomic64_64.h:15 ./include/linux/atomic/atomic-arch-fallback.h:2583 ./include/linux/atomic/atomic-instrumented.h:1611 net/core/sock_diag.c:29)\nbpf_get_socket_ptr_cookie (./arch/x86/include/asm/preempt.h:94 ./include/linux/sock_diag.h:42 net/core/filter.c:5094 net/core/filter.c:5092)\nbpf_prog_875642cf11f1d139___sock_release+0x6e/0x8e\nbpf_trampoline_6442506592+0x47/0xaf\n__sock_release (net/socket.c:652)\n__sock_create (net/socket.c:1601)\n...\nAllocated by task 299 on cpu 2 at 78.328492s:\nkasan_save_stack (mm/kasan/common.c:48)\nkasan_save_track (mm/kasan/common.c:68)\n__kasan_slab_alloc (mm/kasan/common.c:312 mm/kasan/common.c:338)\nkmem_cache_alloc_noprof (mm/slub.c:3941 mm/slub.c:4000 mm/slub.c:4007)\nsk_prot_alloc (net/core/sock.c:2075)\nsk_alloc (net/core/sock.c:2134)\ninet_create (net/ipv4/af_inet.c:327 net/ipv4/af_inet.c:252)\n__sock_create (net/socket.c:1572)\n__sys_socket (net/socket.c:1660 net/socket.c:1644 net/socket.c:1706)\n__x64_sys_socket (net/socket.c:1718)\ndo_syscall_64 (arch/x86/entry/common.c:52 arch/x86/entry/common.c:83)\nentry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)\n\nFreed by task 299 on cpu 2 at 78.328502s:\nkasan_save_stack (mm/kasan/common.c:48)\nkasan_save_track (mm/kasan/common.c:68)\nkasan_save_free_info (mm/kasan/generic.c:582)\npoison_slab_object (mm/kasan/common.c:242)\n__kasan_slab_free (mm/kasan/common.c:256)\nkmem_cache_free (mm/slub.c:4437 mm/slub.c:4511)\n__sk_destruct (net/core/sock.c:2117 net/core/sock.c:2208)\ninet_create (net/ipv4/af_inet.c:397 net/ipv4/af_inet.c:252)\n__sock_create (net/socket.c:1572)\n__sys_socket (net/socket.c:1660 net/socket.c:1644 net/socket.c:1706)\n__x64_sys_socket (net/socket.c:1718)\ndo_syscall_64 (arch/x86/entry/common.c:52 arch/x86/entry/common.c:83)\nentry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)\n\nFix this by clearing the struct socket reference in sk_common_release() to cover\nall protocol families create functions, which may already attached the\nreference to the sk object with sock_init_data()."
                }
            ],
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                        "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
                        "baseScore": 7.8,
                        "baseSeverity": "HIGH"
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                        {
                            "lang": "en",
                            "value": "AV:L - The dangling pointer is created by the local `socket(2)` syscall reaching `__sock_create()` → `inet_create()` and failing after `sock_init_data()`; no packet or remote peer data is involved in reaching the vulnerable code. The dereference likewise happens in the syscalling task's own context.\nAC:L - `ping_init_sock()` returns -EACCES for every user under the kernel-default empty `ping_group_range` ([1,0]), so `socket(AF_INET, SOCK_DGRAM, IPPROTO_ICMP)` frees `sk` and leaves `sock->sk` dangling deterministically on every attempt, with no race to win and no memory layout outside the attacker's influence. On a target running the socket-lifecycle eBPF instrumentation that constitutes the vulnerable configuration, the freed-object access follows unconditionally.\nPR:L - Any ordinary unprivileged local account — including an unprivileged container tenant — can issue the failing `socket()` call; there is no capability check, no user-namespace requirement, and even `traceroute` run by a normal user triggers it. The privileges needed to install the tracing probe belong to the host's monitoring stack, not to the attacker.\nUI:N - The attacker performs the entire sequence with a single syscall from their own process; no other user must open a file, mount anything, or take any action.\nS:U - The freed `struct sock` and the corrupting access are both inside the kernel's own security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - This is a slab use-after-free read of the freed `struct sock` (`atomic64_read(&sk->sk_cookie)` at a controllable offset into a reallocated object), and the value read is returned to the reader — a UAF read of kernel heap contents that can disclose whatever has been sprayed into the reclaimed slot.\nI:H - `__sock_gen_cookie()` does not merely read: with `sk_cookie == 0` it performs an `atomic64_cmpxchg()`, writing 8 bytes into the freed object, so a reallocated victim structure occupying that slot is corrupted at a fixed offset. A use-after-free write into sprayed heap memory is a real corruption primitive with control-flow-hijack potential.\nA:H - The use-after-free reliably produces KASAN slab-use-after-free reports and, on a production kernel, corrupts arbitrary reclaimed slab objects, causing oopses and panics; the trigger can be repeated in a tight loop by an unprivileged user."
                        }
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                }
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