CVE-2026-74544

Full vulnerability record from the local CVENow database.

Description

In the Linux kernel, the following vulnerability has been resolved: net/sched: cls_u32: validate offshift to prevent shift-out-of-bounds u32_change() copies the user-provided tc_u32_sel.offshift (unsigned char, 0-255) into the kernel knode object without bounds validation. When a packet later hits u32_classify() with TC_U32_VAROFFSET set, it evaluates `ntohs(offmask & *data) >> offshift` where the left operand is a 16-bit value promoted to a 32-bit int. Any offshift >= 32 is undefined behavior per C11 6.5.7p3, triggerable by an unprivileged user via user/network namespaces. UBSAN: shift-out-of-bounds in net/sched/cls_u32.c:236:43 shift exponent 32 is too large for 32-bit type int Fix this by rejecting offshift >= 16 during filter creation in u32_change().

Severity

HIGH

CVSS score

7.8 (v3.1)

Vulnerability status

Received

Source identifier

416baaa9-dc9f-4396-8d5f-8c081fb06d67

Published

2026-08-15 13:17:59.753000

Last modified

2026-10-30 13:20:02.290000

View original CVE JSON

{
  "id": "CVE-2026-74544",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "published": "2026-08-15T13:17:59.753",
  "lastModified": "2026-10-30T13:20:02.290",
  "vulnStatus": "Received",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: cls_u32: validate offshift to prevent shift-out-of-bounds\n\nu32_change() copies the user-provided tc_u32_sel.offshift (unsigned char,\n0-255) into the kernel knode object without bounds validation. When a\npacket later hits u32_classify() with TC_U32_VAROFFSET set, it evaluates\n`ntohs(offmask & *data) >> offshift` where the left operand is a 16-bit\nvalue promoted to a 32-bit int. Any offshift >= 32 is undefined behavior\nper C11 6.5.7p3, triggerable by an unprivileged user via user/network\nnamespaces.\n\nUBSAN: shift-out-of-bounds in net/sched/cls_u32.c:236:43\nshift exponent 32 is too large for 32-bit type int\n\nFix this by rejecting offshift >= 16 during filter creation in\nu32_change()."
    }
  ],
  "affected": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "affectedData": [
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "unaffected",
          "programFiles": [
            "net/sched/cls_u32.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "versions": [
            {
              "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
              "lessThan": "7fd5b2287e5cf33e114fb7f0cef781a546039757",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
              "lessThan": "724c8edbacf1259988829cb9967f751222121d8a",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
              "lessThan": "006a4598da9a6b02e0ddc3ca5042b97224774364",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
              "lessThan": "9990cac513e8b191de2ee589051ea7ebf3cee940",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
              "lessThan": "313cb9ffc4101a885d791facf4b5ea3d5e06144d",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
              "lessThan": "aef96eead2860cbfa371e4471d4f04412213b958",
              "versionType": "git",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "affected",
          "programFiles": [
            "net/sched/cls_u32.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "versions": [
            {
              "version": "2.6.12",
              "status": "affected"
            },
            {
              "version": "0",
              "lessThan": "2.6.12",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.1.191",
              "lessThanOrEqual": "6.1.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.6.160",
              "lessThanOrEqual": "6.6.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.12.114",
              "lessThanOrEqual": "6.12.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.18.57",
              "lessThanOrEqual": "6.18.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "7.1.8",
              "lessThanOrEqual": "7.1.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "7.2",
              "lessThanOrEqual": "*",
              "versionType": "original_commit_for_fix",
              "status": "unaffected"
            }
          ]
        }
      ]
    }
  ],
  "metrics": {
    "cvssMetricV31": [
      {
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary",
        "cvssData": {
          "version": "3.1",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
          "baseScore": 7.8,
          "baseSeverity": "HIGH",
          "attackVector": "LOCAL",
          "attackComplexity": "LOW",
          "privilegesRequired": "LOW",
          "userInteraction": "NONE",
          "scope": "UNCHANGED",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "availabilityImpact": "HIGH"
        },
        "exploitabilityScore": 1.8,
        "impactScore": 5.9
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "timestamp": "2026-10-16T18:59:49.230429Z",
          "id": "CVE-2026-74544",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "total"
            }
          ],
          "role": "CISA Coordinator",
          "version": "2.0.3"
        }
      }
    ]
  },
  "references": [
    {
      "url": "https://git.kernel.org/stable/c/006a4598da9a6b02e0ddc3ca5042b97224774364",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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    {
      "url": "https://git.kernel.org/stable/c/9990cac513e8b191de2ee589051ea7ebf3cee940",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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    {
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    }
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}