FKIE_CVE-2026-90050

Vulnerability from fkie_nvd - Published: 2026-09-17 17:16 - Updated: 2026-09-17 17:16
Severity
Summary
In the Linux kernel, the following vulnerability has been resolved: net/sched: fq: clamp quantum and initial_quantum in change path The fq change path accepts TCA_FQ_QUANTUM in [1, INT_MAX] and TCA_FQ_INITIAL_QUANTUM up to INT_MAX, while fq_init() already clamps to [1, 1<<20]. A user can override the init clamp via tc qdisc change, restoring the small-quantum deficit spin that the init clamp prevents. Narrow iq_range.max to 1<<20 so TCA_FQ_INITIAL_QUANTUM is rejected at parse time. Clamp TCA_FQ_QUANTUM to [256, 1<<20] in fq_change() and fq_init() quantum to [256, 1<<20] for tiny-MTU devices. Conditions to recreate the bug: CONFIG_NET_SCH_FQ=y. Requires CAP_NET_ADMIN (namespace-local via unshare -Urn suffices). tc qdisc add dev dummy0 root fq tc qdisc change dev dummy0 root fq quantum 1 stab data 32768 size_log 15 cell_log 0
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/094cc07f98dfe70a34e2a1923af17fd29b8cf622
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/72e9387884554f47b03bfd40fb8b2bf52789c68d
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/798283cd0fe7ba997f67e5a917f14ab40afa8d9f
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/a27498d34c3f429fb6db3aa609569f8154afa175
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/sched/sch_fq.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "a27498d34c3f429fb6db3aa609569f8154afa175",
              "status": "affected",
              "version": "d16dac3925be95ad46e986d4b139c9898b6e227f",
              "versionType": "git"
            },
            {
              "lessThan": "798283cd0fe7ba997f67e5a917f14ab40afa8d9f",
              "status": "affected",
              "version": "f6b3e3848a5fca63438984acd6d9eceac80814c1",
              "versionType": "git"
            },
            {
              "lessThan": "72e9387884554f47b03bfd40fb8b2bf52789c68d",
              "status": "affected",
              "version": "e35acd56f244d94355f9ab237c2ecc8fba5e6f04",
              "versionType": "git"
            },
            {
              "lessThan": "094cc07f98dfe70a34e2a1923af17fd29b8cf622",
              "status": "affected",
              "version": "709f34f7c28dc4dd6c40343d101850f11e172312",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/sched/sch_fq.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "7.3-rc1"
            },
            {
              "lessThan": "7.3-rc1",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3-rc3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: fq: clamp quantum and initial_quantum in change path\n\nThe fq change path accepts TCA_FQ_QUANTUM in [1, INT_MAX] and\nTCA_FQ_INITIAL_QUANTUM up to INT_MAX, while fq_init() already clamps to\n[1, 1\u003c\u003c20]. A user can override the init clamp via tc qdisc change,\nrestoring the small-quantum deficit spin that the init clamp prevents.\n\nNarrow iq_range.max to 1\u003c\u003c20 so TCA_FQ_INITIAL_QUANTUM is rejected at\nparse time. Clamp TCA_FQ_QUANTUM to [256, 1\u003c\u003c20] in fq_change() and\nfq_init() quantum to [256, 1\u003c\u003c20] for tiny-MTU devices.\n\nConditions to recreate the bug:\n  CONFIG_NET_SCH_FQ=y. Requires CAP_NET_ADMIN (namespace-local via\n  unshare -Urn suffices).\n\n  tc qdisc add dev dummy0 root fq\n  tc qdisc change dev dummy0 root fq quantum 1 stab data 32768 size_log 15 cell_log 0"
    }
  ],
  "id": "CVE-2026-90050",
  "lastModified": "2026-09-17T17:16:53.363",
  "metrics": {},
  "published": "2026-09-17T17:16:53.363",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/094cc07f98dfe70a34e2a1923af17fd29b8cf622"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/72e9387884554f47b03bfd40fb8b2bf52789c68d"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/798283cd0fe7ba997f67e5a917f14ab40afa8d9f"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/a27498d34c3f429fb6db3aa609569f8154afa175"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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