CVE-2026-63874 (GCVE-0-2026-63874)

Vulnerability from cvelistv5 – Published: 2026-07-19 14:18 – Updated: 2026-08-05 12:36
VLAI
Title
net: mctp: usb: fix race between urb completion and rx_retry cancellation
Summary
In the Linux kernel, the following vulnerability has been resolved: net: mctp: usb: fix race between urb completion and rx_retry cancellation It's possible that sequencing between setting ->stopped and cancelling the rx_retry work (in ndo_stop) could leave us with an urb queued: T1: ndo_stop T2: rx_retry_work ------------ ---------------- LD: ->stopped => false ST: ->stopped <= true usb_kill_urb() mctp_usb_rx_queue() usb_submit_urb() cancel_delayed_work_sync() That urb completion can then re-schedule rx_retry_work. Strenghen the sequencing between the stop (preventing another requeue) and the cancel by updating both atomically under a new rx lock. After setting ->rx_stopped, and cancelling pending work, we know that the requeue cannot occur, so all that's left is killing any pending urb.
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 0791c0327a6e4e7691d6fc5ad334c215de04dcc9 , < 9c46f3ee1837f6881cb99a52ffecb2760f11dc73 (git)
Affected: 0791c0327a6e4e7691d6fc5ad334c215de04dcc9 , < d90feaa3f74bea8dafb6494631a194c70e547d94 (git)
Affected: 0791c0327a6e4e7691d6fc5ad334c215de04dcc9 , < 54665dce982689e2fd99b32e9a0dcc204fda8a51 (git)
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Linux Linux Affected: 6.15
Unaffected: 0 , < 6.15 (semver)
Unaffected: 6.18.36 , ≤ 6.18.* (semver)
Unaffected: 7.0.13 , ≤ 7.0.* (semver)
Unaffected: 7.1 , ≤ * (original_commit_for_fix)
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/net/mctp/mctp-usb.c"
          ],
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          "vendor": "Linux",
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              "status": "affected",
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              "versionType": "git"
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          "versions": [
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              "version": "0",
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              "versionType": "semver"
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              "operator": "OR"
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: mctp: usb: fix race between urb completion and rx_retry cancellation\n\nIt\u0027s possible that sequencing between setting -\u003estopped and cancelling\nthe rx_retry work (in ndo_stop) could leave us with an urb queued:\n\n    T1: ndo_stop                  T2: rx_retry_work\n    ------------                  ----------------\n                                  LD: -\u003estopped =\u003e false\n    ST: -\u003estopped \u003c= true\n    usb_kill_urb()\n                                  mctp_usb_rx_queue()\n                                    usb_submit_urb()\n    cancel_delayed_work_sync()\n\nThat urb completion can then re-schedule rx_retry_work.\n\nStrenghen the sequencing between the stop (preventing another requeue)\nand the cancel by updating both atomically under a new rx lock. After\nsetting -\u003erx_stopped, and cancelling pending work, we know that the\nrequeue cannot occur, so all that\u0027s left is killing any pending urb."
        }
      ],
      "metrics": [
        {
          "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 race is hit in `mctp_usb_stop()` (`ndo_stop`) during netdev teardown, which is reachable via local RTNETLINK (`ip link set down`) or USB disconnect; it is not reachable from remote network input. Per the uncertainty rule, Local is chosen over Physical.\nAC:L - An attacker can control both sides of the race by inducing RX ENOMEM to schedule `rx_retry_work` (memory pressure) and concurrently triggering netdev stop/disconnect, retrying timing until the window between `stopped=true` and `cancel_delayed_work_sync()` is won.\nPR:L - Triggering `ndo_stop` through RTNETLINK requires `CAP_NET_ADMIN`, which is obtainable in an unprivileged user namespace; a physical USB disconnect path needs no software privileges, but PR:L is the higher-severity choice when uncertain.\nUI:N - Exploitation does not require any victim user action beyond the attacker\u2019s own interface teardown/disconnect and memory-pressure timing.\nS:U - Impact is kernel memory corruption/UAF within the same kernel security boundary, not a cross-boundary escape such as guest-to-host or sandbox breakout.\nC:H - Winning the race leaves RX URBs/completions running after `usb_free_urb()` and `free_netdev()`, producing a use-after-free on `net_device`, `urb`, and `sk_buff` objects that can be turned into arbitrary kernel memory disclosure.\nI:H - The post-teardown UAF on heap-allocated driver/netdev/USB objects provides exploitable write primitives (re-submitted URBs, corrupted completion handlers) suitable for control-flow hijack and privilege escalation.\nA:H - The bug reliably causes kernel crashes (oops/panic) when freed URBs/netdevs are touched by completion handlers or rescheduled `rx_retry_work`, even before full exploitation."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:36:47.817Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
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          "url": "https://git.kernel.org/stable/c/9c46f3ee1837f6881cb99a52ffecb2760f11dc73"
        },
        {
          "url": "https://git.kernel.org/stable/c/d90feaa3f74bea8dafb6494631a194c70e547d94"
        },
        {
          "url": "https://git.kernel.org/stable/c/54665dce982689e2fd99b32e9a0dcc204fda8a51"
        }
      ],
      "title": "net: mctp: usb: fix race between urb completion and rx_retry cancellation",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
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  },
  "cveMetadata": {
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-63874",
    "datePublished": "2026-07-19T14:18:41.907Z",
    "dateReserved": "2026-07-19T07:54:57.017Z",
    "dateUpdated": "2026-08-05T12:36:47.817Z",
    "state": "PUBLISHED"
  },
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  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
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      "date": "2026-09-21",
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      "percentile": "0.07051"
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                "programFiles": [
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          }
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        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: mctp: usb: fix race between urb completion and rx_retry cancellation\n\nIt\u0027s possible that sequencing between setting -\u003estopped and cancelling\nthe rx_retry work (in ndo_stop) could leave us with an urb queued:\n\n    T1: ndo_stop                  T2: rx_retry_work\n    ------------                  ----------------\n                                  LD: -\u003estopped =\u003e false\n    ST: -\u003estopped \u003c= true\n    usb_kill_urb()\n                                  mctp_usb_rx_queue()\n                                    usb_submit_urb()\n    cancel_delayed_work_sync()\n\nThat urb completion can then re-schedule rx_retry_work.\n\nStrenghen the sequencing between the stop (preventing another requeue)\nand the cancel by updating both atomically under a new rx lock. After\nsetting -\u003erx_stopped, and cancelling pending work, we know that the\nrequeue cannot occur, so all that\u0027s left is killing any pending urb."
          }
        ],
        "id": "CVE-2026-63874",
        "lastModified": "2026-07-27T17:44:23.777",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "LOCAL",
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                "baseSeverity": "HIGH",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "LOW",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/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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        "published": "2026-07-19T15:16:54.450",
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            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/54665dce982689e2fd99b32e9a0dcc204fda8a51"
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          }
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        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Awaiting Analysis"
      }
    },
    "redhat_vex": {
      "aggregate_severity": "None",
      "current_release_date": "2026-08-05T14:05:53+00:00",
      "cve": "CVE-2026-63874",
      "id": "CVE-2026-63874",
      "initial_release_date": "2026-07-19T00:00:00+00:00",
      "product_status:known_not_affected": "274",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: net: mctp: usb: fix race between urb completion and rx_retry cancellation",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-63874.json",
      "version": "3"
    }
  }
}



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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.

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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.
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  • 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.


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