ethtool: cmis: require exact CDB reply length

{
  "id": "cec4f4b1107389e011bcb9a79df45e82caa1e671695cca0473700b2faf86d400",
  "url": "https://osv.dev/vulnerability/CVE-2026-63996",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "ethtool: cmis: require exact CDB reply length",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: ethtool: cmis: require exact CDB reply length Malicious SFP module could respond with rpl_len longer than what cmis_cdb_process_reply() expected, leading to OOB writes. Malicious HW is a bit theoretical but some modules may just be buggy and/or the reads may occasionally get corrupted, so let's protect the kernel. The existing check protects from short replies. We need to protect from long ones, too. All callers that pass a non-zero rpl_exp_len cast the reply payload to a fixed-layout struct and read fields at fixed offsets, with no version negotiation or short-reply handling: - cmis_cdb_validate_password() - cmis_cdb_module_features_get() - cmis_fw_update_fw_mng_features_get() so let's assume that responses longer than expected do not have to be handled gracefully here. Add a warning message to make the debug easier in case my understanding is wrong... Note that page_data->length (argument of kmalloc) comes from last arg to ethtool_cmis_page_init() which is rpl_exp_len. Note2 that AIs also like to point out overflows in args->req.payload itself (which is a fixed-size 120 B buffer, on the stack), but callers should be reading structs defined by the standard, so protecting from requests for more data than max seem like defensive programming.",
    "evidence": "osv:CVE-2026-63996",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.12.93",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.35",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "7.0.12",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-63996",
      "aliases": [
        "CVE-2026-63996"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
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                  "introduced": "a39c84d796254e6b1662ca0c46dbc313379e9291"
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                {
                  "fixed": "2f818cc98fd2c63a08239cb48995f6c3bfe9d9b3"
                },
                {
                  "fixed": "4d42fb88ec61f2e98c33a9e3a2de371d5edbc6b1"
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                {
                  "fixed": "eb5dcd740cd7fa27bc2caeff2d28ef28e93ff4d3"
                },
                {
                  "fixed": "6c3f999a9d1338c6c89a9ff4549eafe72bc2e7b1"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-63996.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.11.0"
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                {
                  "fixed": "6.12.93"
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            {
              "type": "ECOSYSTEM",
              "events": [
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                  "introduced": "6.13.0"
                },
                {
                  "fixed": "6.18.35"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.19.0"
                },
                {
                  "fixed": "7.0.12"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-63996.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:29.223502305Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/2f818cc98fd2c63a08239cb48995f6c3bfe9d9b3",
        "https://git.kernel.org/stable/c/4d42fb88ec61f2e98c33a9e3a2de371d5edbc6b1",
        "https://git.kernel.org/stable/c/6c3f999a9d1338c6c89a9ff4549eafe72bc2e7b1",
        "https://git.kernel.org/stable/c/eb5dcd740cd7fa27bc2caeff2d28ef28e93ff4d3",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/63xxx/CVE-2026-63996.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-63996",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/63xxx/CVE-2026-63996.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-63996",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 496294,
  "published_at": "2026-07-19T14:56:15.256+00:00"
}