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CVE-2026-80995 (GCVE-0-2026-80995)

Vulnerability from cvelistv5 – Published: 2026-09-11 19:42 – Updated: 2026-09-13 06:28
VLAI
Title
net: mctp: hold a reference to the route device in mctp_route_lookup()
Summary
In the Linux kernel, the following vulnerability has been resolved: net: mctp: hold a reference to the route device in mctp_route_lookup() mctp_route_lookup() uses rt->dev without holding a reference on it. mctp_route_lookup_single() returns the route under RCU only, so the route's device can be torn down concurrently: mctp_dev_put() drops the last reference and synchronously kfree()s mdev->addrs. mctp_dev_saddr() then reads rt->dev->addrs[0], giving a use-after-free reachable by an unprivileged local AF_MCTP user on the receive/forwarding path (no CAP_NET_RAW required): BUG: KASAN: slab-use-after-free in mctp_route_lookup Read of size 1 at addr ... by task mctp_uaf/... mctp_route_lookup mctp_pkttype_receive Freed by task ...: kfree mctp_dev_put mctp_dev_notify In the same window mctp_dst_from_route() -> mctp_dev_hold() also increments a refcount that has already reached zero ("refcount_t: addition on 0 ... mctp_dev_hold"). This reintroduces the use-after-free class of CVE-2023-3439: the source address lookup was moved ahead of the point where the destination takes its device reference. Take a reference with refcount_inc_not_zero() before touching rt->dev, skip a device that is already dead, and drop the reference once the destination has taken its own.
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: 22cb45afd221b9e4f2a1dcc74a8ff645b7293aa1 , < cc561f8af25586300c2f9d285babb163b866b293 (git)
Affected: 22cb45afd221b9e4f2a1dcc74a8ff645b7293aa1 , < 408da1df18116c971c3392e21e50586688cd3fbf (git)
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Linux Linux Affected: 7.1
Unaffected: 0 , < 7.1 (semver)
Unaffected: 7.2.4 , ≤ 7.2.* (semver)
Unaffected: 7.3-rc1 , ≤ * (original_commit_for_fix)
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/mctp/route.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "status": "affected",
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                  "vulnerable": true
                },
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: mctp: hold a reference to the route device in mctp_route_lookup()\n\nmctp_route_lookup() uses rt-\u003edev without holding a reference on it.\nmctp_route_lookup_single() returns the route under RCU only, so the\nroute\u0027s device can be torn down concurrently: mctp_dev_put() drops the\nlast reference and synchronously kfree()s mdev-\u003eaddrs.  mctp_dev_saddr()\nthen reads rt-\u003edev-\u003eaddrs[0], giving a use-after-free reachable by an\nunprivileged local AF_MCTP user on the receive/forwarding path (no\nCAP_NET_RAW required):\n\n  BUG: KASAN: slab-use-after-free in mctp_route_lookup\n  Read of size 1 at addr ... by task mctp_uaf/...\n   mctp_route_lookup\n   mctp_pkttype_receive\n  Freed by task ...:\n   kfree\n   mctp_dev_put\n   mctp_dev_notify\n\nIn the same window mctp_dst_from_route() -\u003e mctp_dev_hold() also\nincrements a refcount that has already reached zero\n(\"refcount_t: addition on 0 ... mctp_dev_hold\").\n\nThis reintroduces the use-after-free class of CVE-2023-3439: the source\naddress lookup was moved ahead of the point where the destination takes\nits device reference.\n\nTake a reference with refcount_inc_not_zero() before touching rt-\u003edev,\nskip a device that is already dead, and drop the reference once the\ndestination has taken its own."
        }
      ],
      "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": [
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              "lang": "en",
              "value": "AV:L - The UAF is reached when mctp_pkttype_receive() calls mctp_route_lookup() while the route device is destroyed via mctp_dev_notify()/NETDEV_UNREGISTER. An unprivileged local user can create a TUN (ARPHRD_NONE auto-attaches mctp_dev), inject ETH_P_MCTP frames, and delete that netdev; this is a local syscall/netlink path, not a remote IP service.\nAC:L - The attacker controls both sides of the race by injecting MCTP packets on one thread and unregistering the TUN/MCTP netdev on another, and can retry until mctp_dev_saddr() runs after mctp_dev_put() has synchronously kfree\u0027d mdev-\u003eaddrs.\nPR:L - TUN creation, MCTP address/route setup, and netdev teardown require CAP_NET_ADMIN, which an unprivileged user obtains in a user+net namespace. The receive/forwarding path has no CAP_NET_RAW check, unlike mctp_sendmsg().\nUI:N - Exploitation requires no victim action; the attacker alone creates the interface, injects frames, and tears it down.\nS:U - Impact is in-kernel use-after-free and local privilege escalation within the same kernel security authority; no VM escape, IOMMU bypass, or sandbox boundary is crossed.\nC:H - This is a use-after-free of mdev-\u003eaddrs (and a dangling mctp_dev after refcount-add-on-0); UAF of a kmalloc object enables heap reuse and arbitrary kernel memory disclosure.\nI:H - After the last reference is dropped, mctp_dst_from_route() still calls mctp_dev_hold() and later dst.output() uses the freed device; reclaiming that object yields an arbitrary write and control-flow hijack primitive.\nA:H - KASAN reports a slab-use-after-free in mctp_route_lookup and a refcount_t addition-on-0 in mctp_dev_hold; the UAF reliably oopses or panics the kernel even when not fully exploited."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-13T06:28:58.816Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/cc561f8af25586300c2f9d285babb163b866b293"
        },
        {
          "url": "https://git.kernel.org/stable/c/408da1df18116c971c3392e21e50586688cd3fbf"
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      "title": "net: mctp: hold a reference to the route device in mctp_route_lookup()",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-80995",
    "datePublished": "2026-09-11T19:42:50.866Z",
    "dateReserved": "2026-08-26T14:34:25.812Z",
    "dateUpdated": "2026-09-13T06:28:58.816Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
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      "date": "2026-09-15",
      "epss": "0.0012",
      "percentile": "0.02099"
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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-09-14T20:16:15+00:00",
      "cve": "CVE-2026-80995",
      "id": "CVE-2026-80995",
      "initial_release_date": "2026-09-11T00:00:00+00:00",
      "product_status:known_not_affected": "276",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: net: mctp: hold a reference to the route device in mctp_route_lookup()",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-80995.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "important",
      "current_release_date": "2026-09-13T17:00:16Z",
      "cve": "CVE-2026-80995",
      "id": "CVE-2026-80995",
      "initial_release_date": "2026-09-12T16:36:00Z",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-80995",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-80995.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.

Sightings

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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.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • 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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