Vulnerability-Lookup

FKIE_CVE-2026-43392

Vulnerability from fkie_nvd - Published: 2026-05-08 15:16 - Updated: 2026-05-26 14:55

Severity

5.5 (Medium) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

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.

References

URL	Tags
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/05ab9ec5dc24f234e0a2fecf3e6ff937c68f7d81	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/b06ccbabe2506fd70b9167a644978b049150224a	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/c44198f25fdfecc0ec0fe366bf8a47fe17d8e229	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/e0b14bf06393be137d3efb6a3b7cd5b4b9810a6b	Patch

Impacted products

Vendor	Product	Version
linux	linux_kernel	*
linux	linux_kernel	*
linux	linux_kernel	*
linux	linux_kernel	6.12
linux	linux_kernel	6.12
linux	linux_kernel	6.12
linux	linux_kernel	6.12
linux	linux_kernel	6.12
linux	linux_kernel	6.12
linux	linux_kernel	6.12
linux	linux_kernel	7.0
linux	linux_kernel	7.0

JSON

To clipboard

{
  "configurations": [
    {
      "nodes": [
        {
          "cpeMatch": [
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              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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              "versionEndExcluding": "6.12.78",
              "versionStartIncluding": "6.12.1",
              "vulnerable": true
            },
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              "matchCriteriaId": "E5571059-6552-48E7-9BEF-3E358C387171",
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  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "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."
    }
  ],
  "id": "CVE-2026-43392",
  "lastModified": "2026-05-26T14:55:03.500",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "LOCAL",
          "availabilityImpact": "HIGH",
          "baseScore": 5.5,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "privilegesRequired": "LOW",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 1.8,
        "impactScore": 3.6,
        "source": "nvd@nist.gov",
        "type": "Primary"
      }
    ]
  },
  "published": "2026-05-08T15:16:50.583",
  "references": [
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      "tags": [
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    },
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  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "NVD-CWE-noinfo"
        }
      ],
      "source": "nvd@nist.gov",
      "type": "Primary"
    }
  ]
}

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

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)

Show details on NVD website

JSON

To clipboard

{
  "containers": {
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      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "kernel/sched/ext.c"
          ],
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          "vendor": "Linux",
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    "cveId": "CVE-2026-43392",
    "datePublished": "2026-05-08T14:21:36.692Z",
    "dateReserved": "2026-05-01T14:12:56.007Z",
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}

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

FKIE_CVE-2026-43392

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

Tags

Sightings

Nomenclature