FKIE_CVE-2026-90076

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: add overflow bounds to quantum and initial quantum fq_init() computes quantum = 2 * psched_mtu() and initial_quantum = 10 * psched_mtu() with no overflow check. A device with a huge MTU (e.g. dummy with max_mtu == 0 accepting MTU 2147483634) makes psched_mtu() return 0x80000000; the 2 * and 10 * multiplications wrap to 0 in 32-bit arithmetic, so q->quantum == 0. Then in fq_dequeue() the credit-refill loop adds 0 to f->credit (which stays <= 0) and goto begin loops forever under the qdisc lock, creating a soft lockup. Clamp psched_mtu() to [1, 1 << 20] before multiplying so the product cannot wrap, then cap the result at 1 << 20, matching the bound already enforced on TCA_FQ_QUANTUM in fq_change(). Conditions to recreate the bug: a device whose MTU (plus hard_header_len) is large enough that 2 * psched_mtu() wraps (e.g. a dummy device with max_mtu == 0 accepting MTU 2147483634). Requires CAP_NET_ADMIN in a user namespace.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/709f34f7c28dc4dd6c40343d101850f11e172312
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/d16dac3925be95ad46e986d4b139c9898b6e227f
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/e35acd56f244d94355f9ab237c2ecc8fba5e6f04
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/f6b3e3848a5fca63438984acd6d9eceac80814c1
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": "d16dac3925be95ad46e986d4b139c9898b6e227f",
              "status": "affected",
              "version": "afe4fd062416b158a8a8538b23adc1930a9b88dc",
              "versionType": "git"
            },
            {
              "lessThan": "f6b3e3848a5fca63438984acd6d9eceac80814c1",
              "status": "affected",
              "version": "afe4fd062416b158a8a8538b23adc1930a9b88dc",
              "versionType": "git"
            },
            {
              "lessThan": "e35acd56f244d94355f9ab237c2ecc8fba5e6f04",
              "status": "affected",
              "version": "afe4fd062416b158a8a8538b23adc1930a9b88dc",
              "versionType": "git"
            },
            {
              "lessThan": "709f34f7c28dc4dd6c40343d101850f11e172312",
              "status": "affected",
              "version": "afe4fd062416b158a8a8538b23adc1930a9b88dc",
              "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": "3.12"
            },
            {
              "lessThan": "3.12",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.110",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.52",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.6",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3-rc1",
              "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: add overflow bounds to quantum and initial quantum\n\nfq_init() computes quantum = 2 * psched_mtu() and initial_quantum = 10 *\npsched_mtu() with no overflow check. A device with a huge MTU (e.g. dummy\nwith max_mtu == 0 accepting MTU 2147483634) makes psched_mtu() return\n0x80000000; the 2 * and 10 * multiplications wrap to 0 in 32-bit\narithmetic, so q-\u003equantum == 0. Then in fq_dequeue() the credit-refill\nloop adds 0 to f-\u003ecredit (which stays \u003c= 0) and goto begin loops\nforever under the qdisc lock, creating a soft lockup.\n\nClamp psched_mtu() to [1, 1 \u003c\u003c 20] before multiplying so the product\ncannot wrap, then cap the result at 1 \u003c\u003c 20, matching the bound already\nenforced on TCA_FQ_QUANTUM in fq_change().\n\nConditions to recreate the bug: a device whose MTU (plus\nhard_header_len) is large enough that 2 * psched_mtu() wraps (e.g. a\ndummy device with max_mtu == 0 accepting MTU 2147483634). Requires\nCAP_NET_ADMIN in a user namespace."
    }
  ],
  "id": "CVE-2026-90076",
  "lastModified": "2026-09-17T17:16:56.820",
  "metrics": {},
  "published": "2026-09-17T17:16:56.820",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/709f34f7c28dc4dd6c40343d101850f11e172312"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/d16dac3925be95ad46e986d4b139c9898b6e227f"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/e35acd56f244d94355f9ab237c2ecc8fba5e6f04"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/f6b3e3848a5fca63438984acd6d9eceac80814c1"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.





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

Author Source Type Date Other

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.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.