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GHSA-QWMC-GMGX-XF8H

Vulnerability from github – Published: 2026-10-18 18:32 – Updated: 2026-10-18 18:32

Details

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

futex: Fix private hash use-after-free on resize

poll_state_synchronize_rcu(mm->futex.phash.batches) is used by futex_ref_drop() to check that a grace period has passed since the current hash was published. This relies on batches referencing a grace period which started after the hash pointer was assigned.

__futex_pivot_hash() sets mmph->batches before it replaces mmph->hash:

scoped_guard(rcu) {
        mmph->batches = get_state_synchronize_rcu();
        rcu_assign_pointer(mmph->hash, new);
}

The scoped_guard(rcu) doesn't stop new grace periods from starting, and if one starts between those two assignments, futex_ref_drop() can move forward while a reader still holds a pointer to the old hash.

Fix things by setting mmph->batches after assigning mmph->hash. The scoped_guard(rcu) isn't needed, so let's drop that as well.

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{
  "affected": [],
  "aliases": [
    "CVE-2026-98788"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-10-18T16:17:32Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nfutex: Fix private hash use-after-free on resize\n\npoll_state_synchronize_rcu(mm-\u003efutex.phash.batches) is used by\nfutex_ref_drop() to check that a grace period has passed since the\ncurrent hash was published. This relies on batches referencing a grace\nperiod which started after the hash pointer was assigned.\n\n__futex_pivot_hash() sets mmph-\u003ebatches before it replaces mmph-\u003ehash:\n\n    scoped_guard(rcu) {\n            mmph-\u003ebatches = get_state_synchronize_rcu();\n            rcu_assign_pointer(mmph-\u003ehash, new);\n    }\n\nThe scoped_guard(rcu) doesn\u0027t stop new grace periods from starting, and\nif one starts between those two assignments, futex_ref_drop() can move\nforward while a reader still holds a pointer to the old hash.\n\nFix things by setting mmph-\u003ebatches after assigning mmph-\u003ehash.  The\nscoped_guard(rcu) isn\u0027t needed, so let\u0027s drop that as well.",
  "id": "GHSA-qwmc-gmgx-xf8h",
  "modified": "2026-10-18T18:32:03Z",
  "published": "2026-10-18T18:32:03Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98788"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/5d5dc18b3a9ac011619b7d3af4514bf9e9b6a6af"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/f35e3b5784221654f9cdbd6222275a7fa203f6c3"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}

CVE-2026-98788 (GCVE-0-2026-98788)

Vulnerability from cvelistv5 – Published: 2026-10-18 15:48 – Updated: 2026-10-19 09:25

Title

futex: Fix private hash use-after-free on resize

Summary

In the Linux kernel, the following vulnerability has been resolved: futex: Fix private hash use-after-free on resize poll_state_synchronize_rcu(mm->futex.phash.batches) is used by futex_ref_drop() to check that a grace period has passed since the current hash was published. This relies on batches referencing a grace period which started after the hash pointer was assigned. __futex_pivot_hash() sets mmph->batches before it replaces mmph->hash: scoped_guard(rcu) { mmph->batches = get_state_synchronize_rcu(); rcu_assign_pointer(mmph->hash, new); } The scoped_guard(rcu) doesn't stop new grace periods from starting, and if one starts between those two assignments, futex_ref_drop() can move forward while a reader still holds a pointer to the old hash. Fix things by setting mmph->batches after assigning mmph->hash. The scoped_guard(rcu) isn't needed, so let's drop that as well.

Severity

No CVSS data available.

Assigner

Linux CNA under the mitre root

CNA scorecard D 53/100 over 6820 records in the last 180 days details

References

2 references

URL	Tags
https://git.kernel.org/stable/c/5d5dc18b3a9ac0116…
https://git.kernel.org/stable/c/f35e3b5784221654f…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 56180dd20c19e5b0fa34822997a9ac66b517e7b3 , < 5d5dc18b3a9ac011619b7d3af4514bf9e9b6a6af (git) Affected: 56180dd20c19e5b0fa34822997a9ac66b517e7b3 , < f35e3b5784221654f9cdbd6222275a7fa203f6c3 (git)
Linux	Linux	Affected: 6.17 Unaffected: 0 , < 6.17 (semver) Unaffected: 7.2.10 , ≤ 7.2.* (semver) Unaffected: 7.3 , ≤ * (original_commit_for_fix)

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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "kernel/futex/core.c"
          ],
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          "vendor": "Linux",
          "versions": [
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            },
            {
              "lessThan": "f35e3b5784221654f9cdbd6222275a7fa203f6c3",
              "status": "affected",
              "version": "56180dd20c19e5b0fa34822997a9ac66b517e7b3",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "kernel/futex/core.c"
          ],
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          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
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              "version": "0",
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              "status": "unaffected",
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              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
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              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
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          "nodes": [
            {
              "cpeMatch": [
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                  "vulnerable": true
                },
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                }
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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nfutex: Fix private hash use-after-free on resize\n\npoll_state_synchronize_rcu(mm-\u003efutex.phash.batches) is used by\nfutex_ref_drop() to check that a grace period has passed since the\ncurrent hash was published. This relies on batches referencing a grace\nperiod which started after the hash pointer was assigned.\n\n__futex_pivot_hash() sets mmph-\u003ebatches before it replaces mmph-\u003ehash:\n\n    scoped_guard(rcu) {\n            mmph-\u003ebatches = get_state_synchronize_rcu();\n            rcu_assign_pointer(mmph-\u003ehash, new);\n    }\n\nThe scoped_guard(rcu) doesn\u0027t stop new grace periods from starting, and\nif one starts between those two assignments, futex_ref_drop() can move\nforward while a reader still holds a pointer to the old hash.\n\nFix things by setting mmph-\u003ebatches after assigning mmph-\u003ehash.  The\nscoped_guard(rcu) isn\u0027t needed, so let\u0027s drop that as well."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T09:25:41.209Z",
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    "datePublished": "2026-10-18T15:48:24.833Z",
    "dateReserved": "2026-09-25T10:25:14.370Z",
    "dateUpdated": "2026-10-19T09:25:41.209Z",
    "state": "PUBLISHED"
  },
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}

Sightings

Author	Source	Type	Date	Other

Nomenclature

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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.

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