{
  "schema_version": "1.6.1",
  "id": "RPI-CVE-2024-49855",
  "modified": "2026-10-09T11:39:44Z",
  "upstream": [
    "CVE-2024-49855"
  ],
  "published": "2024-10-21T12:19:03Z",
  "summary": "nbd: fix race between timeout and normal completion",
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnbd: fix race between timeout and normal completion\n\nIf request timetout is handled by nbd_requeue_cmd(), normal completion\nhas to be stopped for avoiding to complete this requeued request, other\nuse-after-free can be triggered.\n\nFix the race by clearing NBD_CMD_INFLIGHT in nbd_requeue_cmd(), meantime\nmake sure that cmd->lock is grabbed for clearing the flag and the\nrequeue.",
  "severity": [
    {
      "type": "CVSS_V3",
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
    }
  ],
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  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.cve.org/CVERecord?id=CVE-2024-49855"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/9c25faf72d780a9c71081710cd48759d61ff6e9b"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/6e73b946a379a1dfbb62626af93843bdfb53753d"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/5236ada8ebbd9e7461f17477357582f5be4f46f7"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/9a74c3e6c0d686c26ba2aab66d15ddb89dc139cc"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/c9ea57c91f03bcad415e1a20113bdb2077bcf990"
    }
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  "database_specific": {
    "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git",
    "upstream_modified": "2026-08-05T11:52:36Z",
    "severity": {
      "source": "kernel CNA",
      "cvss_v3_score": 9.8,
      "cvss_v3_severity": "Critical",
      "scenario": "AV:N - The race is driven by the NBD reply stream received over TCP in `recv_work()`/`nbd_handle_reply()`, code that processes data from a remote peer; a malicious or compromised NBD server \u2014 or an on-path attacker, since the NBD protocol is plaintext and unauthenticated on port 10809 \u2014 controls reply timing and content.\nAC:L - The remote server controls both sides of the race: it withholds a reply to force `nbd_xmit_timeout()` to fire, then delivers the reply at that instant to collide with `nbd_requeue_cmd()`, and it can repeat this across many in-flight requests indefinitely at no cost.\nPR:N - The NBD protocol carries no authentication, so the attacking server or MITM needs no credentials or privileges on the victim host; the CAP_SYS_ADMIN gate only covers the victim admin's own legitimate `nbd-client` setup, which is a pre-existing deployment condition rather than an attacker privilege.\nUI:N - No victim action is needed at attack time \u2014 an already-established NBD session (diskless boot, cloud block storage) is enough, and a compromised server or on-path attacker triggers the race unilaterally.\nS:U - The use-after-free and block-layer corruption stay within the kernel of the affected host; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - Re-dispatching an already-completed request makes `nbd_send_cmd()` walk freed bio/bvec memory and transmit its contents over the socket to the attacker-controlled server, directly disclosing freed kernel/page-cache data.\nI:H - A re-dispatched READ writes the server's attacker-chosen reply payload into freed and possibly reallocated pages, and the requeue of a reused request corrupts `q->requeue_list`/`rq->queuelist` \u2014 a controlled write primitive usable for control-flow hijacking.\nA:H - The double completion and requeue of a freed/reused request reliably produce list corruption, KASAN use-after-free splats, oops, or hang of the storage path and the machine."
    }
  }
}