CVE-2026-98012 (GCVE-0-2026-98012)

Vulnerability from cvelistv5 – Published: 2026-09-25 10:23 – Updated: 2026-09-25 10:23
VLAI
Title
net/sched: sfq: clamp quantum in change path
Summary
In the Linux kernel, the following vulnerability has been resolved: net/sched: sfq: clamp quantum in change path sfq_change() accepts any non-negative quantum (only rejects (int)ctl->quantum < 0). With a crafted size table qdisc_pkt_len reaches ~2 GiB, so quantum=1 makes the deficit-refill loop spin ~2^31 times under the qdisc lock (a soft lockup / denial of service). Add max(256U, ...) matching fq_codel_change(). Reject quantum > 1<<20 with -EINVAL, matching fq_codel_change() and the init clamp. Conditions to recreate the bug: CONFIG_NET_SCH_SFQ=y. Requires CAP_NET_ADMIN (namespace-local via unshare -Urn suffices). tc qdisc add dev dummy0 root sfq tc qdisc change dev dummy0 root sfq 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: 82bd38bd5467ece1ee274b493f51326cf5220a5a , < f3820dce042a673fcb28cc31c87ee14257e21a17 (git)
Affected: e4650d7ae4252f67e997a632adfae0dd74d3a99a , < 534cd7ecbbc6e8a974f4003a5c1557439c6e0a72 (git)
Affected: e4650d7ae4252f67e997a632adfae0dd74d3a99a , < e6c1cb728e389354203a72bc77464c222a247aeb (git)
Affected: e4650d7ae4252f67e997a632adfae0dd74d3a99a , < fb9f88a33c516ea5c0bcd9a22ca288b246b34567 (git)
Affected: 843cacb88f42f426973f1ed11c6fb562558efb27 (git)
Affected: 4919649699c5f4dbae08b8e2ed536fc9d6c3c2aa (git)
Affected: 548cf048b426729a7a1fa6acd1271c010c9a7380 (git)
Affected: c49ac48fac51a6a54efd5963954d02bacf075085 (git)
Affected: 58ae7465f0e7113d45aa88a66bf2d203c71c195e (git)
Affected: 6.12.13 , < 6.12.111 (semver)
Affected: 5.4.297 , < 5.5 (semver)
Affected: 5.10.239 , < 5.11 (semver)
Affected: 5.15.186 , < 5.16 (semver)
Affected: 6.1.129 , < 6.2 (semver)
Affected: 6.6.76 , < 6.7 (semver)
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Linux Linux Affected: 6.13
Unaffected: 0 , < 6.13 (semver)
Unaffected: 6.12.111 , ≤ 6.12.* (semver)
Unaffected: 6.18.53 , ≤ 6.18.* (semver)
Unaffected: 7.2.7 , ≤ 7.2.* (semver)
Unaffected: 7.3-rc3 , ≤ * (original_commit_for_fix)
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    "dateReserved": "2026-09-25T10:19:56.069Z",
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            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: sfq: clamp quantum in change path\n\nsfq_change() accepts any non-negative quantum (only rejects\n(int)ctl-\u003equantum \u003c 0). With a crafted size table qdisc_pkt_len reaches\n~2 GiB, so quantum=1 makes the deficit-refill loop spin ~2^31 times\nunder the qdisc lock (a soft lockup / denial of service).\n\nAdd max(256U, ...) matching fq_codel_change(). Reject quantum \u003e 1\u003c\u003c20\nwith -EINVAL, matching fq_codel_change() and the init clamp.\n\nConditions to recreate the bug:\n  CONFIG_NET_SCH_SFQ=y. Requires CAP_NET_ADMIN (namespace-local via\n  unshare -Urn suffices).\n\n  tc qdisc add dev dummy0 root sfq\n  tc qdisc change dev dummy0 root sfq quantum 1 stab data 32768 size_log 15 cell_log 0"
          }
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        "id": "CVE-2026-98012",
        "lastModified": "2026-09-25T11:17:29.537",
        "metrics": {},
        "published": "2026-09-25T11:17:29.537",
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        "vulnStatus": "Received"
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    }
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}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
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