Vulnerability-Lookup

GHSA-VWW6-HVWF-MV33

Vulnerability from github – Published: 2026-05-08 15:31 – Updated: 2026-05-26 15:32

Details

In the Linux kernel, the following vulnerability has been resolved:

sched_ext: Fix starvation of scx_enable() under fair-class saturation

During scx_enable(), the READY -> ENABLED task switching loop changes the calling thread's sched_class from fair to ext. Since fair has higher priority than ext, saturating fair-class workloads can indefinitely starve the enable thread, hanging the system. This was introduced when the enable path switched from preempt_disable() to scx_bypass() which doesn't protect against fair-class starvation. Note that the original preempt_disable() protection wasn't complete either - in partial switch modes, the calling thread could still be starved after preempt_enable() as it may have been switched to ext class.

Fix it by offloading the enable body to a dedicated system-wide RT (SCHED_FIFO) kthread which cannot be starved by either fair or ext class tasks. scx_enable() lazily creates the kthread on first use and passes the ops pointer through a struct scx_enable_cmd containing the kthread_work, then synchronously waits for completion.

The workfn runs on a different kthread from sch->helper (which runs disable_work), so it can safely flush disable_work on the error path without deadlock.

Severity

5.5 (Medium)


                  
                    CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

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{
  "affected": [],
  "aliases": [
    "CVE-2026-43392"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-05-08T15:16:50Z",
    "severity": "MODERATE"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nsched_ext: Fix starvation of scx_enable() under fair-class saturation\n\nDuring scx_enable(), the READY -\u003e ENABLED task switching loop changes the\ncalling thread\u0027s sched_class from fair to ext. Since fair has higher\npriority than ext, saturating fair-class workloads can indefinitely starve\nthe enable thread, hanging the system. This was introduced when the enable\npath switched from preempt_disable() to scx_bypass() which doesn\u0027t protect\nagainst fair-class starvation. Note that the original preempt_disable()\nprotection wasn\u0027t complete either - in partial switch modes, the calling\nthread could still be starved after preempt_enable() as it may have been\nswitched to ext class.\n\nFix it by offloading the enable body to a dedicated system-wide RT\n(SCHED_FIFO) kthread which cannot be starved by either fair or ext class\ntasks. scx_enable() lazily creates the kthread on first use and passes the\nops pointer through a struct scx_enable_cmd containing the kthread_work,\nthen synchronously waits for completion.\n\nThe workfn runs on a different kthread from sch-\u003ehelper (which runs\ndisable_work), so it can safely flush disable_work on the error path\nwithout deadlock.",
  "id": "GHSA-vww6-hvwf-mv33",
  "modified": "2026-05-26T15:32:08Z",
  "published": "2026-05-08T15:31:27Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-43392"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/05ab9ec5dc24f234e0a2fecf3e6ff937c68f7d81"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/b06ccbabe2506fd70b9167a644978b049150224a"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/c44198f25fdfecc0ec0fe366bf8a47fe17d8e229"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/e0b14bf06393be137d3efb6a3b7cd5b4b9810a6b"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2026-43392 (GCVE-0-2026-43392)

Vulnerability from cvelistv5 – Published: 2026-05-08 14:21 – Updated: 2026-05-11 22:23

Title

sched_ext: Fix starvation of scx_enable() under fair-class saturation

Summary

In the Linux kernel, the following vulnerability has been resolved: sched_ext: Fix starvation of scx_enable() under fair-class saturation During scx_enable(), the READY -> ENABLED task switching loop changes the calling thread's sched_class from fair to ext. Since fair has higher priority than ext, saturating fair-class workloads can indefinitely starve the enable thread, hanging the system. This was introduced when the enable path switched from preempt_disable() to scx_bypass() which doesn't protect against fair-class starvation. Note that the original preempt_disable() protection wasn't complete either - in partial switch modes, the calling thread could still be starved after preempt_enable() as it may have been switched to ext class. Fix it by offloading the enable body to a dedicated system-wide RT (SCHED_FIFO) kthread which cannot be starved by either fair or ext class tasks. scx_enable() lazily creates the kthread on first use and passes the ops pointer through a struct scx_enable_cmd containing the kthread_work, then synchronously waits for completion. The workfn runs on a different kthread from sch->helper (which runs disable_work), so it can safely flush disable_work on the error path without deadlock.

Severity

No CVSS data available.

Assigner

Linux

References

4 references

URL	Tags
https://git.kernel.org/stable/c/e0b14bf06393be137…
https://git.kernel.org/stable/c/c44198f25fdfecc0e…
https://git.kernel.org/stable/c/05ab9ec5dc24f234e…
https://git.kernel.org/stable/c/b06ccbabe2506fd70…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 8c2090c504e998c8f34ec870bae71dafcc96a6e0 , < e0b14bf06393be137d3efb6a3b7cd5b4b9810a6b (git) Affected: 8c2090c504e998c8f34ec870bae71dafcc96a6e0 , < c44198f25fdfecc0ec0fe366bf8a47fe17d8e229 (git) Affected: 8c2090c504e998c8f34ec870bae71dafcc96a6e0 , < 05ab9ec5dc24f234e0a2fecf3e6ff937c68f7d81 (git) Affected: 8c2090c504e998c8f34ec870bae71dafcc96a6e0 , < b06ccbabe2506fd70b9167a644978b049150224a (git)
Linux	Linux	Affected: 6.12 Unaffected: 0 , < 6.12 (semver) Unaffected: 6.12.78 , ≤ 6.12.* (semver) Unaffected: 6.18.20 , ≤ 6.18.* (semver) Unaffected: 6.19.9 , ≤ 6.19.* (semver) Unaffected: 7.0 , ≤ * (original_commit_for_fix)

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JSON

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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "kernel/sched/ext.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "e0b14bf06393be137d3efb6a3b7cd5b4b9810a6b",
              "status": "affected",
              "version": "8c2090c504e998c8f34ec870bae71dafcc96a6e0",
              "versionType": "git"
            },
            {
              "lessThan": "c44198f25fdfecc0ec0fe366bf8a47fe17d8e229",
              "status": "affected",
              "version": "8c2090c504e998c8f34ec870bae71dafcc96a6e0",
              "versionType": "git"
            },
            {
              "lessThan": "05ab9ec5dc24f234e0a2fecf3e6ff937c68f7d81",
              "status": "affected",
              "version": "8c2090c504e998c8f34ec870bae71dafcc96a6e0",
              "versionType": "git"
            },
            {
              "lessThan": "b06ccbabe2506fd70b9167a644978b049150224a",
              "status": "affected",
              "version": "8c2090c504e998c8f34ec870bae71dafcc96a6e0",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "kernel/sched/ext.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.12"
            },
            {
              "lessThan": "6.12",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.78",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.20",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.19.*",
              "status": "unaffected",
              "version": "6.19.9",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.0",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.78",
                  "versionStartIncluding": "6.12",
                  "vulnerable": true
                },
                {
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsched_ext: Fix starvation of scx_enable() under fair-class saturation\n\nDuring scx_enable(), the READY -\u003e ENABLED task switching loop changes the\ncalling thread\u0027s sched_class from fair to ext. Since fair has higher\npriority than ext, saturating fair-class workloads can indefinitely starve\nthe enable thread, hanging the system. This was introduced when the enable\npath switched from preempt_disable() to scx_bypass() which doesn\u0027t protect\nagainst fair-class starvation. Note that the original preempt_disable()\nprotection wasn\u0027t complete either - in partial switch modes, the calling\nthread could still be starved after preempt_enable() as it may have been\nswitched to ext class.\n\nFix it by offloading the enable body to a dedicated system-wide RT\n(SCHED_FIFO) kthread which cannot be starved by either fair or ext class\ntasks. scx_enable() lazily creates the kthread on first use and passes the\nops pointer through a struct scx_enable_cmd containing the kthread_work,\nthen synchronously waits for completion.\n\nThe workfn runs on a different kthread from sch-\u003ehelper (which runs\ndisable_work), so it can safely flush disable_work on the error path\nwithout deadlock."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-05-11T22:23:41.885Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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          "url": "https://git.kernel.org/stable/c/05ab9ec5dc24f234e0a2fecf3e6ff937c68f7d81"
        },
        {
          "url": "https://git.kernel.org/stable/c/b06ccbabe2506fd70b9167a644978b049150224a"
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-43392",
    "datePublished": "2026-05-08T14:21:36.692Z",
    "dateReserved": "2026-05-01T14:12:56.007Z",
    "dateUpdated": "2026-05-11T22:23:41.885Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

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.

Detection rules are retrieved from Rulezet.

Action not permitted

GHSA-VWW6-HVWF-MV33

CVE-2026-43392 (GCVE-0-2026-43392)

Tags

Sightings

Nomenclature