CVE-2026-43323 (GCVE-0-2026-43323)

Vulnerability from cvelistv5 – Published: 2026-05-08 13:31 – Updated: 2026-05-08 13:31
VLAI?
Title
sched/fair: Fix zero_vruntime tracking fix
Summary
In the Linux kernel, the following vulnerability has been resolved: sched/fair: Fix zero_vruntime tracking fix John reported that stress-ng-yield could make his machine unhappy and managed to bisect it to commit b3d99f43c72b ("sched/fair: Fix zero_vruntime tracking"). The combination of yield and that commit was specific enough to hypothesize the following scenario: Suppose we have 2 runnable tasks, both doing yield. Then one will be eligible and one will not be, because the average position must be in between these two entities. Therefore, the runnable task will be eligible, and be promoted a full slice (all the tasks do is yield after all). This causes it to jump over the other task and now the other task is eligible and current is no longer. So we schedule. Since we are runnable, there is no {de,en}queue. All we have is the __{en,de}queue_entity() from {put_prev,set_next}_task(). But per the fingered commit, those two no longer move zero_vruntime. All that moves zero_vruntime are tick and full {de,en}queue. This means, that if the two tasks playing leapfrog can reach the critical speed to reach the overflow point inside one tick's worth of time, we're up a creek. Additionally, when multiple cgroups are involved, there is no guarantee the tick will in fact hit every cgroup in a timely manner. Statistically speaking it will, but that same statistics does not rule out the possibility of one cgroup not getting a tick for a significant amount of time -- however unlikely. Therefore, just like with the yield() case, force an update at the end of every slice. This ensures the update is never more than a single slice behind and the whole thing is within 2 lag bounds as per the comment on entity_key().
Severity ?
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: d2fc2dcfce47a56ffd414783003cc966c742c8a9 , < c089147074ed96ff4330739a0559394c19a3dfc8 (git)
Affected: 99673934a89febe664e704550216638dcb2336a8 , < 87573883c30f1a8555ff720836bb6ea231058539 (git)
Affected: 978d4fe59665c13db692ba96839f9c52d69f13f3 , < fb61ffb3fb30a161eb5404c27fc7635e275beafd (git)
Affected: b3d99f43c72b56cf7a104a364e7fb34b0702828b , < 1319ea57529e131822bab56bf417c8edc2db9ae8 (git)
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    Linux Linux Affected: 6.12.78 , < 6.12.81 (semver)
Affected: 6.18.17 , < 6.18.22 (semver)
Affected: 6.19.7 , < 6.19.12 (semver)
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          "product": "Linux",
          "programFiles": [
            "kernel/sched/fair.c"
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              "operator": "OR"
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsched/fair: Fix zero_vruntime tracking fix\n\nJohn reported that stress-ng-yield could make his machine unhappy and\nmanaged to bisect it to commit b3d99f43c72b (\"sched/fair: Fix\nzero_vruntime tracking\").\n\nThe combination of yield and that commit was specific enough to\nhypothesize the following scenario:\n\nSuppose we have 2 runnable tasks, both doing yield. Then one will be\neligible and one will not be, because the average position must be in\nbetween these two entities.\n\nTherefore, the runnable task will be eligible, and be promoted a full\nslice (all the tasks do is yield after all). This causes it to jump over\nthe other task and now the other task is eligible and current is no\nlonger. So we schedule.\n\nSince we are runnable, there is no {de,en}queue. All we have is the\n__{en,de}queue_entity() from {put_prev,set_next}_task(). But per the\nfingered commit, those two no longer move zero_vruntime.\n\nAll that moves zero_vruntime are tick and full {de,en}queue.\n\nThis means, that if the two tasks playing leapfrog can reach the\ncritical speed to reach the overflow point inside one tick\u0027s worth of\ntime, we\u0027re up a creek.\n\nAdditionally, when multiple cgroups are involved, there is no guarantee\nthe tick will in fact hit every cgroup in a timely manner. Statistically\nspeaking it will, but that same statistics does not rule out the\npossibility of one cgroup not getting a tick for a significant amount of\ntime -- however unlikely.\n\nTherefore, just like with the yield() case, force an update at the end\nof every slice. This ensures the update is never more than a single\nslice behind and the whole thing is within 2 lag bounds as per the\ncomment on entity_key()."
        }
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        "dateUpdated": "2026-05-08T13:31:08.188Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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          "url": "https://git.kernel.org/stable/c/c089147074ed96ff4330739a0559394c19a3dfc8"
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        },
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          "url": "https://git.kernel.org/stable/c/fb61ffb3fb30a161eb5404c27fc7635e275beafd"
        },
        {
          "url": "https://git.kernel.org/stable/c/1319ea57529e131822bab56bf417c8edc2db9ae8"
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      ],
      "title": "sched/fair: Fix zero_vruntime tracking fix",
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    "cveId": "CVE-2026-43323",
    "datePublished": "2026-05-08T13:31:08.188Z",
    "dateReserved": "2026-05-01T14:12:56.001Z",
    "dateUpdated": "2026-05-08T13:31:08.188Z",
    "state": "PUBLISHED"
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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.

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  • Confirmed: The vulnerability has been validated from an analyst's perspective.
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  • 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.



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