CVE-2025-21972 (GCVE-0-2025-21972)
Vulnerability from cvelistv5
Published
2025-04-01 15:47
Modified
2026-08-05 11:55
Severity ?
8.8 (High) - CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: net: mctp: unshare packets when reassembling Ensure that the frag_list used for reassembly isn't shared with other packets. This avoids incorrect reassembly when packets are cloned, and prevents a memory leak due to circular references between fragments and their skb_shared_info. The upcoming MCTP-over-USB driver uses skb_clone which can trigger the problem - other MCTP drivers don't share SKBs. A kunit test is added to reproduce the issue.
References
Impacted products
Vendor Product Version
Linux Linux Version: 4a992bbd365094730a31bae1e12a6ca695336d57
Version: 4a992bbd365094730a31bae1e12a6ca695336d57
Version: 4a992bbd365094730a31bae1e12a6ca695336d57
 Create a notification for this product.
Show details on NVD website

To clipboard 

{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/mctp/route.c",
            "net/mctp/test/route-test.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "5c47d5bfa7b096cf8890afac32141c578583f8e0",
              "status": "affected",
              "version": "4a992bbd365094730a31bae1e12a6ca695336d57",
              "versionType": "git"
            },
            {
              "lessThan": "f44fff3d3c6cd67b6f348b821d73c4d6888c7a6e",
              "status": "affected",
              "version": "4a992bbd365094730a31bae1e12a6ca695336d57",
              "versionType": "git"
            },
            {
              "lessThan": "f5d83cf0eeb90fade4d5c4d17d24b8bee9ceeecc",
              "status": "affected",
              "version": "4a992bbd365094730a31bae1e12a6ca695336d57",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/mctp/route.c",
            "net/mctp/test/route-test.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "5.15"
            },
            {
              "lessThan": "5.15",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.20",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.13.*",
              "status": "unaffected",
              "version": "6.13.8",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "6.14",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.20",
                  "versionStartIncluding": "5.15",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.13.8",
                  "versionStartIncluding": "5.15",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.14",
                  "versionStartIncluding": "5.15",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "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\u0027t 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\u0027t share SKBs.\n\nA kunit test is added to reproduce the issue."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 8.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "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."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T11:55:47.567Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/5c47d5bfa7b096cf8890afac32141c578583f8e0"
        },
        {
          "url": "https://git.kernel.org/stable/c/f44fff3d3c6cd67b6f348b821d73c4d6888c7a6e"
        },
        {
          "url": "https://git.kernel.org/stable/c/f5d83cf0eeb90fade4d5c4d17d24b8bee9ceeecc"
        }
      ],
      "title": "net: mctp: unshare packets when reassembling",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2025-21972",
    "datePublished": "2025-04-01T15:47:04.960Z",
    "dateReserved": "2024-12-29T08:45:45.797Z",
    "dateUpdated": "2026-08-05T11:55:47.567Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


Log in or create an account to share your comment.




Tags
Taxonomy of the tags.




Sightings

Author Source Type Date

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
  • Confirmed: The vulnerability is confirmed from an analyst perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
  • Patched: This vulnerability was successfully patched by the user reporting the sighting.
  • Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
  • Not confirmed: The user expresses doubt about the veracity of the vulnerability.
  • Not patched: This vulnerability was not successfully patched by the user reporting the sighting.