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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntcp: Fix refcnt handling in __inet_hash_connect().\n\nsyzbot reported a warning in sk_nulls_del_node_init_rcu().\n\nThe commit 66b60b0c8c4a (\"dccp/tcp: Unhash sk from ehash for tb2 alloc\nfailure after check_estalblished().\") tried to fix an issue that an\nunconnected socket occupies an ehash entry when bhash2 allocation fails.\n\nIn such a case, we need to revert changes done by check_established(),\nwhich does not hold refcnt when inserting socket into ehash.\n\nSo, to revert the change, we need to __sk_nulls_add_node_rcu() instead\nof sk_nulls_add_node_rcu().\n\nOtherwise, sock_put() will cause refcnt underflow and leak the socket.\n\n[0]:\nWARNING: CPU: 0 PID: 23948 at include/net/sock.h:799 sk_nulls_del_node_init_rcu+0x166/0x1a0 include/net/sock.h:799\nModules linked in:\nCPU: 0 PID: 23948 Comm: syz-executor.2 Not tainted 6.8.0-rc6-syzkaller-00159-gc055fc00c07b #0\nHardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024\nRIP: 0010:sk_nulls_del_node_init_rcu+0x166/0x1a0 include/net/sock.h:799\nCode: e8 7f 71 c6 f7 83 fb 02 7c 25 e8 35 6d c6 f7 4d 85 f6 0f 95 c0 5b 41 5c 41 5d 41 5e 41 5f 5d c3 cc cc cc cc e8 1b 6d c6 f7 90 \u003c0f\u003e 0b 90 eb b2 e8 10 6d c6 f7 4c 89 e7 be 04 00 00 00 e8 63 e7 d2\nRSP: 0018:ffffc900032d7848 EFLAGS: 00010246\nRAX: ffffffff89cd0035 RBX: 0000000000000001 RCX: 0000000000040000\nRDX: ffffc90004de1000 RSI: 000000000003ffff RDI: 0000000000040000\nRBP: 1ffff1100439ac26 R08: ffffffff89ccffe3 R09: 1ffff1100439ac28\nR10: dffffc0000000000 R11: ffffed100439ac29 R12: ffff888021cd6140\nR13: dffffc0000000000 R14: ffff88802a9bf5c0 R15: ffff888021cd6130\nFS:  00007f3b823f16c0(0000) GS:ffff8880b9400000(0000) knlGS:0000000000000000\nCS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033\nCR2: 00007f3b823f0ff8 CR3: 000000004674a000 CR4: 00000000003506f0\nDR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000\nDR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400\nCall Trace:\n \u003cTASK\u003e\n __inet_hash_connect+0x140f/0x20b0 net/ipv4/inet_hashtables.c:1139\n dccp_v6_connect+0xcb9/0x1480 net/dccp/ipv6.c:956\n __inet_stream_connect+0x262/0xf30 net/ipv4/af_inet.c:678\n inet_stream_connect+0x65/0xa0 net/ipv4/af_inet.c:749\n __sys_connect_file net/socket.c:2048 [inline]\n __sys_connect+0x2df/0x310 net/socket.c:2065\n __do_sys_connect net/socket.c:2075 [inline]\n __se_sys_connect net/socket.c:2072 [inline]\n __x64_sys_connect+0x7a/0x90 net/socket.c:2072\n do_syscall_64+0xf9/0x240\n entry_SYSCALL_64_after_hwframe+0x6f/0x77\nRIP: 0033:0x7f3b8167dda9\nCode: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 \u003c48\u003e 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48\nRSP: 002b:00007f3b823f10c8 EFLAGS: 00000246 ORIG_RAX: 000000000000002a\nRAX: ffffffffffffffda RBX: 00007f3b817abf80 RCX: 00007f3b8167dda9\nRDX: 000000000000001c RSI: 0000000020000040 RDI: 0000000000000003\nRBP: 00007f3b823f1120 R08: 0000000000000000 R09: 0000000000000000\nR10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001\nR13: 000000000000000b R14: 00007f3b817abf80 R15: 00007ffd3beb57b8\n \u003c/TASK\u003e"
        }
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      "metrics": [
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          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The vulnerable code is reached through the local `connect(2)` syscall path (`__sys_connect` \u2192 `inet_stream_connect` \u2192 `tcp_v4/v6_connect`/`dccp_v4/v6_connect` \u2192 `__inet_hash_connect`), requiring a local socket the attacker owns. A remote peer cannot initiate this path directly, though MPTCP subflow creation triggered by a peer\u0027s ADD_ADDR reaches it indirectly.\nAC:L - The attacker controls both preconditions: the unprivileged `IP_LOCAL_PORT_RANGE` sockopt pins the ephemeral range so the `check_established()` branch is taken deterministically, and the GFP_ATOMIC bhash2 allocation failure is driven by attacker-created memory/slab pressure while `connect()` is retried in an unbounded loop. Nothing depends on a third party or on state the attacker cannot influence.\nPR:L - Any unprivileged local user can create a TCP/DCCP socket, set `IP_LOCAL_PORT_RANGE`, and call `connect()`; no capability check exists anywhere along the path, and additional local addresses to force a new bhash2 bucket are obtainable inside an unprivileged user namespace (`unshare -Urn`).\nUI:N - The attacking process performs the entire sequence itself via socket syscalls; no victim action, mount, or file open is required.\nS:U - The refcount underflow corrupts kernel socket state within the same kernel security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - The unbalanced `__sock_put()` is a refcount-underflow primitive that, where a second reference holder exists (e.g. MPTCP subflows that `sock_hold()` before `kernel_connect()`), frees the `tcp_sock`/subflow while it is still linked in `msk-\u003econn_list`, giving a use-after-free that can be groomed to read reallocated slab contents and kernel pointers.\nI:H - The same premature free yields a use-after-free on a large, attacker-influenceable `tcp_sock` object containing function pointers (`sk_prot`, `sk_data_ready`, `icsk_af_ops`), which heap spraying can convert into an arbitrary write and control-flow hijack.\nA:H - The path triggers a `WARN_ON` in `sk_nulls_del_node_init_rcu()` plus a `refcount_dec()` underflow warning \u2014 an immediate panic on kernels with `panic_on_warn` \u2014 and otherwise permanently leaks the socket along with its pinned network-namespace reference, repeatable by an unprivileged user until memory is exhausted."
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      "title": "tcp: Fix refcnt handling in __inet_hash_connect().",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2024-26864",
    "datePublished": "2024-04-17T10:27:26.884Z",
    "dateReserved": "2024-02-19T14:20:24.184Z",
    "dateUpdated": "2026-08-05T11:27:52.447Z",
    "state": "PUBLISHED"
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}