{
  "schema_version": "1.6.1",
  "id": "RPI-CVE-2025-21972",
  "modified": "2026-10-09T11:39:44Z",
  "upstream": [
    "CVE-2025-21972"
  ],
  "published": "2025-04-01T15:46:27Z",
  "summary": "net: mctp: unshare packets when reassembling",
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: mctp: unshare packets when reassembling\n\nEnsure that the frag_list used for reassembly isn't shared with other\npackets. This avoids incorrect reassembly when packets are cloned, and\nprevents a memory leak due to circular references between fragments and\ntheir skb_shared_info.\n\nThe upcoming MCTP-over-USB driver uses skb_clone which can trigger the\nproblem - other MCTP drivers don't share SKBs.\n\nA kunit test is added to reproduce the issue.",
  "severity": [
    {
      "type": "CVSS_V3",
      "score": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
    }
  ],
  "affected": [
    {
      "package": {
        "ecosystem": "Raspberry Pi OS:12",
        "name": "linux"
      },
      "versions": [
        "1:6.1.47-1+rpt4"
      ],
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-2712",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v6",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v7",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v7l",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v8",
            "binary_version": "1:6.1.47-1+rpt4"
          }
        ]
      },
      "database_specific": {
        "per_version": {
          "1:6.1.47-1+rpt4": {
            "linux_commit": "655fc658a15ae7a6f37103754adb39ba52a9a14e",
            "upstream_version": "6.1.47",
            "assessment": "commit ancestry (strak rule)",
            "upstream_fixed": null,
            "compiled_filter": false
          }
        }
      }
    }
  ],
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.cve.org/CVERecord?id=CVE-2025-21972"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/5c47d5bfa7b096cf8890afac32141c578583f8e0"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/f44fff3d3c6cd67b6f348b821d73c4d6888c7a6e"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/f5d83cf0eeb90fade4d5c4d17d24b8bee9ceeecc"
    }
  ],
  "database_specific": {
    "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git",
    "upstream_modified": "2026-08-05T12:19:11Z",
    "severity": {
      "source": "kernel CNA",
      "cvss_v3_score": 8.8,
      "cvss_v3_severity": "High",
      "scenario": "AV:A - The vulnerable code is a network-stack packet handler (`ETH_P_MCTP` packet_type \u2192 `mctp_route_input`), but MCTP has no internet-routable transport in the kernel \u2014 packets arrive from a device on the local management bus (SMBus/I2C, I3C, USB, serial), a limited administrative domain directly analogous to the Bluetooth/WiFi case.\nAC:L - The attacker fully controls both preconditions: sending a multi-packet (SOM/EOM) fragmented message, and causing the skbs to be clones by packing several MCTP packets into a single transfer (`mctp-usb.c:219`). No race, memory-layout dependency, or victim state is involved, and the kunit reproducer added by the fix triggers it deterministically.\nPR:N - There is no authentication or authorization anywhere on the path from `mctp_pkttype_receive()` to `mctp_frag_queue()` \u2014 MCTP packets are parsed and reassembled purely on header contents, so a device on the bus needs no credentials or local account.\nUI:N - Reassembly happens in softirq context on packet receive; no user action is needed on the victim system beyond having MCTP configured, which is the normal state for the affected BMC/host management deployments.\nS:U - The corruption and its consequences are confined to kernel skb structures within the same security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - Writing the reassembly `frag_list` into a shared `skb_shared_info` cross-links skbs belonging to different reassembly contexts and to other subsystems (e.g. AF_PACKET clones), so a socket can be delivered a fragment chain from an unrelated message with mismatched length accounting \u2014 memory-state corruption leveragable for disclosure of data from another context.\nI:H - The bug both delivers incorrectly reassembled message content to MCTP sockets (corrupting PLDM/NVMe-MI/NC-SI management traffic) and plants an attacker-influenced skb pointer into a `skb_shared_info` owned by other subsystems, which is later dereferenced and freed by an owner that never expected a fragment list.\nA:H - Every cloned fragmented message permanently leaks its skbs and backing data buffer through the circular `frag_list`/`dataref` reference, and the attacker can repeat this without limit \u2014 driving memory exhaustion and OOM/kernel failure on the memory-constrained BMC and embedded systems where MCTP is deployed."
    }
  }
}