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GHSA-FMHG-FFQ7-4RM5

Vulnerability from github – Published: 2026-10-06 09:31 – Updated: 2026-10-06 09:31

Details

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

sched_ext: Close the pre-enable ops error claim window

scx_alloc_and_add_sched() publishes ops->priv before scx_root_enable_workfn() switches the state to SCX_ENABLING. An error claimed via scx_bpf_error_bstr() from an associated BPF program in that window is consumed by scx_disable_workfn(), which takes the pre-enable shortcut in scx_root_disable(). The shortcut returns without any teardown and restores SCX_DISABLED with an unconditional scx_set_enable_state() xchg racing the enable workfn's own transition. The enable then completes with the claim consumed: the scheduler stays up but can never be disabled again, and bpf_scx_unreg() frees it while still in use, resulting in a use-after-free. Both WARN_ON_ONCE()s fire back to back:

WARNING: kernel/sched/ext/ext.c:7522 at scx_root_enable_workfn+0xeec/0x1be0, CPU#3: scx_enable_help/276

WARNING: kernel/sched/ext/ext.c:6398 at scx_root_disable+0xb50/0xdb8, CPU#0: sched_ext_helpe/664

scx_root_enable_workfn() switches to SCX_ENABLING before the scheduler allocation, so ops->priv is never visible while SCX_DISABLED. The allocation failure path restores SCX_DISABLED.

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{
  "affected": [],
  "aliases": [
    "CVE-2026-98219"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-10-06T09:18:08Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nsched_ext: Close the pre-enable ops error claim window\n\nscx_alloc_and_add_sched() publishes ops-\u003epriv before\nscx_root_enable_workfn() switches the state to SCX_ENABLING. An error\nclaimed via scx_bpf_error_bstr() from an associated BPF program in that\nwindow is consumed by scx_disable_workfn(), which takes the pre-enable\nshortcut in scx_root_disable(). The shortcut returns without any teardown\nand restores SCX_DISABLED with an unconditional scx_set_enable_state() xchg\nracing the enable workfn\u0027s own transition. The enable then completes with\nthe claim consumed: the scheduler stays up but can never be disabled again,\nand bpf_scx_unreg() frees it while still in use, resulting in a\nuse-after-free. Both WARN_ON_ONCE()s fire back to back:\n\n  WARNING: kernel/sched/ext/ext.c:7522 at\n  scx_root_enable_workfn+0xeec/0x1be0, CPU#3: scx_enable_help/276\n\n  WARNING: kernel/sched/ext/ext.c:6398 at scx_root_disable+0xb50/0xdb8,\n  CPU#0: sched_ext_helpe/664\n\nscx_root_enable_workfn() switches to SCX_ENABLING before the scheduler\nallocation, so ops-\u003epriv is never visible while SCX_DISABLED. The allocation\nfailure path restores SCX_DISABLED.",
  "id": "GHSA-fmhg-ffq7-4rm5",
  "modified": "2026-10-06T09:31:31Z",
  "published": "2026-10-06T09:31:31Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98219"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/959c66dc4a915be306c35691095c787c61dc7df9"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/c7a1c6e8004ab12a9c9bfdcb603f60f9bf4a3cee"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}

CVE-2026-98219 (GCVE-0-2026-98219)

Vulnerability from cvelistv5 – Published: 2026-10-06 08:44 – Updated: 2026-10-06 08:44

Title

sched_ext: Close the pre-enable ops error claim window

Summary

In the Linux kernel, the following vulnerability has been resolved: sched_ext: Close the pre-enable ops error claim window scx_alloc_and_add_sched() publishes ops->priv before scx_root_enable_workfn() switches the state to SCX_ENABLING. An error claimed via scx_bpf_error_bstr() from an associated BPF program in that window is consumed by scx_disable_workfn(), which takes the pre-enable shortcut in scx_root_disable(). The shortcut returns without any teardown and restores SCX_DISABLED with an unconditional scx_set_enable_state() xchg racing the enable workfn's own transition. The enable then completes with the claim consumed: the scheduler stays up but can never be disabled again, and bpf_scx_unreg() frees it while still in use, resulting in a use-after-free. Both WARN_ON_ONCE()s fire back to back: WARNING: kernel/sched/ext/ext.c:7522 at scx_root_enable_workfn+0xeec/0x1be0, CPU#3: scx_enable_help/276 WARNING: kernel/sched/ext/ext.c:6398 at scx_root_disable+0xb50/0xdb8, CPU#0: sched_ext_helpe/664 scx_root_enable_workfn() switches to SCX_ENABLING before the scheduler allocation, so ops->priv is never visible while SCX_DISABLED. The allocation failure path restores SCX_DISABLED.

Severity

No CVSS data available.

Assigner

Linux CNA under the mitre root

CNA scorecard D 54/100 over 6633 records in the last 180 days details

References

2 references

URL	Tags
https://git.kernel.org/stable/c/959c66dc4a915be30…
https://git.kernel.org/stable/c/c7a1c6e8004ab12a9…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 105dcd005be2ac1d5541921db8feb1d0f98d59d5 , < 959c66dc4a915be306c35691095c787c61dc7df9 (git) Affected: 105dcd005be2ac1d5541921db8feb1d0f98d59d5 , < c7a1c6e8004ab12a9c9bfdcb603f60f9bf4a3cee (git)
Linux	Linux	Affected: 7.1 Unaffected: 0 , < 7.1 (semver) Unaffected: 7.2.8 , ≤ 7.2.* (semver) Unaffected: 7.3-rc4 , ≤ * (original_commit_for_fix)

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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "kernel/sched/ext/ext.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "959c66dc4a915be306c35691095c787c61dc7df9",
              "status": "affected",
              "version": "105dcd005be2ac1d5541921db8feb1d0f98d59d5",
              "versionType": "git"
            },
            {
              "lessThan": "c7a1c6e8004ab12a9c9bfdcb603f60f9bf4a3cee",
              "status": "affected",
              "version": "105dcd005be2ac1d5541921db8feb1d0f98d59d5",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "kernel/sched/ext/ext.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "7.1"
            },
            {
              "lessThan": "7.1",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.8",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3-rc4",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.8",
                  "versionStartIncluding": "7.1",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3-rc4",
                  "versionStartIncluding": "7.1",
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                }
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              "negate": false,
              "operator": "OR"
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      "descriptions": [
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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsched_ext: Close the pre-enable ops error claim window\n\nscx_alloc_and_add_sched() publishes ops-\u003epriv before\nscx_root_enable_workfn() switches the state to SCX_ENABLING. An error\nclaimed via scx_bpf_error_bstr() from an associated BPF program in that\nwindow is consumed by scx_disable_workfn(), which takes the pre-enable\nshortcut in scx_root_disable(). The shortcut returns without any teardown\nand restores SCX_DISABLED with an unconditional scx_set_enable_state() xchg\nracing the enable workfn\u0027s own transition. The enable then completes with\nthe claim consumed: the scheduler stays up but can never be disabled again,\nand bpf_scx_unreg() frees it while still in use, resulting in a\nuse-after-free. Both WARN_ON_ONCE()s fire back to back:\n\n  WARNING: kernel/sched/ext/ext.c:7522 at\n  scx_root_enable_workfn+0xeec/0x1be0, CPU#3: scx_enable_help/276\n\n  WARNING: kernel/sched/ext/ext.c:6398 at scx_root_disable+0xb50/0xdb8,\n  CPU#0: sched_ext_helpe/664\n\nscx_root_enable_workfn() switches to SCX_ENABLING before the scheduler\nallocation, so ops-\u003epriv is never visible while SCX_DISABLED. The allocation\nfailure path restores SCX_DISABLED."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-06T08:44:54.943Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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      "references": [
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          "url": "https://git.kernel.org/stable/c/959c66dc4a915be306c35691095c787c61dc7df9"
        },
        {
          "url": "https://git.kernel.org/stable/c/c7a1c6e8004ab12a9c9bfdcb603f60f9bf4a3cee"
        }
      ],
      "title": "sched_ext: Close the pre-enable ops error claim window",
      "x_generator": {
        "engine": "bippy-1.2.0"
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    }
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  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-98219",
    "datePublished": "2026-10-06T08:44:54.943Z",
    "dateReserved": "2026-09-25T10:25:14.327Z",
    "dateUpdated": "2026-10-06T08:44:54.943Z",
    "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.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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GHSA-FMHG-FFQ7-4RM5

CVE-2026-98219 (GCVE-0-2026-98219)

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