CVE-2026-89743 (GCVE-0-2026-89743)
Vulnerability from cvelistv5
Published
2026-09-11 19:46
Modified
2026-10-19 08:51
Severity ?
7.7 (High) - CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: misc: nsm: bound the device-reported response length nsm_sendrecv_msg_locked() stores the virtqueue used-ring length reported by the NSM device into msg->resp.len without bounding it to the response buffer. A malicious or buggy backend can report a length larger than the response buffer; parse_resp_raw() then copies that many bytes out of the fixed buffer to user space, disclosing adjacent kernel heap (an out-of-bounds read). The request path already floors its length in fill_req_raw(); the response path lacks the symmetric check. Clamp the stored length to the size of the response buffer. Well-behaved devices report no more than the posted buffer size, so conforming traffic is unaffected.
References
Impacted products
Vendor Product Version
Linux Linux Version: b9873755a6c8ccfce79094c4dce9efa3ecb1a749
Version: b9873755a6c8ccfce79094c4dce9efa3ecb1a749
Version: b9873755a6c8ccfce79094c4dce9efa3ecb1a749
Version: b9873755a6c8ccfce79094c4dce9efa3ecb1a749
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/misc/nsm.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "versionType": "git"
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            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "drivers/misc/nsm.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.8"
            },
            {
              "lessThan": "6.8",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.109",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.50",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.4",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.109",
                  "versionStartIncluding": "6.8",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.50",
                  "versionStartIncluding": "6.8",
                  "vulnerable": true
                },
                {
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                  "versionEndExcluding": "7.2.4",
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                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3",
                  "versionStartIncluding": "6.8",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmisc: nsm: bound the device-reported response length\n\nnsm_sendrecv_msg_locked() stores the virtqueue used-ring length reported\nby the NSM device into msg-\u003eresp.len without bounding it to the response\nbuffer. A malicious or buggy backend can report a length larger than the\nresponse buffer; parse_resp_raw() then copies that many bytes out of the\nfixed buffer to user space, disclosing adjacent kernel heap (an\nout-of-bounds read). The request path already floors its length in\nfill_req_raw(); the response path lacks the symmetric check.\n\nClamp the stored length to the size of the response buffer. Well-behaved\ndevices report no more than the posted buffer size, so conforming traffic\nis unaffected."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.7,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - A malicious or buggy virtio-nsm backend (hypervisor, QEMU virtio-nsm, or vhost-user device) over-reports the used-ring length consumed by nsm_sendrecv_msg_locked(); the path is local ioctl on /dev/nsm plus virtio, not a network protocol.\nAC:L - The backend deterministically sets the 32-bit used-ring length on each completion, and a local NSM_IOCTL_RAW caller supplies the response iovec that parse_resp_raw() uses as the other copy bound; no race or attacker-uncontrollable layout is required.\nPR:N - The driver registers /dev/nsm as mode 0666 and nsm_dev_ioctl() has no capable() check, so any local process can issue NSM_IOCTL_RAW; a malicious virtio backend also needs no guest credentials.\nUI:N - The attacker opens /dev/nsm and issues NSM_IOCTL_RAW from their own process (the ioctl does not cap response.len to NSM_RESPONSE_MAX_SIZE); no separate victim must mount, click, or otherwise interact.\nS:U - The out-of-bounds read and any resulting oops occur in the guest kernel that hosts the NSM frontend; this is device-to-guest impact, not a guest-to-host, IOMMU, or cross-VM escape.\nC:H - parse_resp_raw() copy_to_user() copies min(user_len, unbounded device len) from the 0x3000-byte resp-\u003edata array, so an over-reported length reads adjacent kmalloc heap and returns that kernel memory to userspace.\nI:N - The oversized copy writes only into the ioctl caller\u0027s userspace buffer; kernel memory is only read, with no out-of-bounds write, use-after-free, or control-flow hijack primitive.\nA:H - A device-chosen length up to 4GiB drives copy_to_user() past the nsm slab object into unmapped or guarded memory, causing a guest kernel oops or panic that can be repeated on every NSM request."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T08:51:57.186Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/339f19b9a6171289b0e797deb8bda80b9a1fcc30"
        },
        {
          "url": "https://git.kernel.org/stable/c/29e634a18957acda11383a15ab98a91c4ae9e294"
        },
        {
          "url": "https://git.kernel.org/stable/c/2aa0fb9c96f894a9c179a48e7522ea6705800adf"
        },
        {
          "url": "https://git.kernel.org/stable/c/808e530654a5354e6df78863a5d61e4d44e67235"
        }
      ],
      "title": "misc: nsm: bound the device-reported response length",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89743",
    "datePublished": "2026-09-11T19:46:49.261Z",
    "dateReserved": "2026-09-11T19:38:34.761Z",
    "dateUpdated": "2026-10-19T08:51:57.186Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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