mptcp: pm: userspace: fix use-after-free in get_local_id

{
  "id": "d721b2a08c7442a57e6dcb91764f6efff2ee2d6a68dfd2277bc5cb96f5286d51",
  "url": "https://osv.dev/vulnerability/CVE-2026-68169",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "mptcp: pm: userspace: fix use-after-free in get_local_id",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: mptcp: pm: userspace: fix use-after-free in get_local_id In mptcp_pm_userspace_get_local_id(), the address entry is looked up under spinlock, but its id is read after dropping the lock. A concurrent deletion can free the entry between the unlock and the read, leading to UAF. The race window is narrow. It was reproduced only with a locally constructed stress test that repeatedly overlaps an MP_JOIN SYN with a MPTCP_PM_CMD_SUBFLOW_DESTROY request. However, the KASAN report below confirms that the race is reachable: [ 666.319376] BUG: KASAN: slab-use-after-free in mptcp_userspace_pm_get_local_id+0x1dc/0x1f0 [ 666.319386] Read of size 1 at addr ffff888124845610 by task swapper/0/0 ... [ 666.319401] Call Trace: [ 666.319405] [ 666.319408] dump_stack_lvl+0x53/0x70 [ 666.319412] print_address_description.constprop.0+0x2c/0x3b0 [ 666.319418] print_report+0xbe/0x2b0 [ 666.319421] ? mptcp_userspace_pm_get_local_id+0x1dc/0x1f0 [ 666.319423] kasan_report+0xce/0x100 [ 666.319426] ? mptcp_userspace_pm_get_local_id+0x1dc/0x1f0 [ 666.319429] mptcp_userspace_pm_get_local_id+0x1dc/0x1f0 [ 666.319433] mptcp_pm_get_local_id+0x371/0x440 ... [ 666.319821] Allocated by task 45539: [ 666.319844] kasan_save_stack+0x33/0x60 [ 666.319855] kasan_save_track+0x14/0x30 [ 666.319858] __kasan_kmalloc+0x8f/0xa0 [ 666.319863] __kmalloc_noprof+0x1e7/0x520 [ 666.319867] sock_kmalloc+0xdf/0x130 [ 666.319885] sock_kmemdup+0x1b/0x40 [ 666.319888] m",
    "evidence": "osv:CVE-2026-68169",
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          "evidence": "/affected/1/package/name"
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    "severity": "unknown",
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      "modified": "2026-10-08T02:51:37.340680774Z",
      "provider": "osv",
      "references": [
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        "https://git.kernel.org/stable/c/40dde4b5d98279471a70e5c8bb713182738c00d9",
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        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/68xxx/CVE-2026-68169.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-68169",
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  "source_id": "core-osv",
  "document_id": 98326,
  "published_at": "2026-08-10T11:59:38.177+00:00"
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