CVE-2026-90050 (GCVE-0-2026-90050)

Vulnerability from cvelistv5 – Published: 2026-09-17 16:05 – Updated: 2026-09-17 16:05
VLAI
Title
net/sched: fq: clamp quantum and initial_quantum in change path
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
Severity
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: d16dac3925be95ad46e986d4b139c9898b6e227f , < a27498d34c3f429fb6db3aa609569f8154afa175 (git)
Affected: f6b3e3848a5fca63438984acd6d9eceac80814c1 , < 798283cd0fe7ba997f67e5a917f14ab40afa8d9f (git)
Affected: e35acd56f244d94355f9ab237c2ecc8fba5e6f04 , < 72e9387884554f47b03bfd40fb8b2bf52789c68d (git)
Affected: 709f34f7c28dc4dd6c40343d101850f11e172312 , < 094cc07f98dfe70a34e2a1923af17fd29b8cf622 (git)
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Linux Linux Affected: 7.3-rc1
Unaffected: 0 , < 7.3-rc1 (semver)
Unaffected: 7.3-rc3 , ≤ * (original_commit_for_fix)
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{
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      "affected": [
        {
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          "product": "Linux",
          "programFiles": [
            "net/sched/sch_fq.c"
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          "versions": [
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          "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"
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-17T16:05:36.970Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
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          "url": "https://git.kernel.org/stable/c/a27498d34c3f429fb6db3aa609569f8154afa175"
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        },
        {
          "url": "https://git.kernel.org/stable/c/094cc07f98dfe70a34e2a1923af17fd29b8cf622"
        }
      ],
      "title": "net/sched: fq: clamp quantum and initial_quantum in change path",
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  },
  "cveMetadata": {
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-90050",
    "datePublished": "2026-09-17T16:05:36.970Z",
    "dateReserved": "2026-09-11T19:38:34.783Z",
    "dateUpdated": "2026-09-17T16:05:36.970Z",
    "state": "PUBLISHED"
  },
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      "date": "2026-09-25",
      "epss": "0.00209",
      "percentile": "0.0986"
    },
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                "vendor": "Linux",
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                    "versionType": "git"
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                  }
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        "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",
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            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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            "url": "https://git.kernel.org/stable/c/798283cd0fe7ba997f67e5a917f14ab40afa8d9f"
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            "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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