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

Vulnerability from cvelistv5 – Published: 2026-10-18 15:48 – Updated: 2026-10-19 09:25
VLAI
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
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 56180dd20c19e5b0fa34822997a9ac66b517e7b3 , < 5d5dc18b3a9ac011619b7d3af4514bf9e9b6a6af (git)
Affected: 56180dd20c19e5b0fa34822997a9ac66b517e7b3 , < f35e3b5784221654f9cdbd6222275a7fa203f6c3 (git)
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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": {
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          "product": "Linux",
          "programFiles": [
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              "operator": "OR"
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          "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",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
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          "url": "https://git.kernel.org/stable/c/5d5dc18b3a9ac011619b7d3af4514bf9e9b6a6af"
        },
        {
          "url": "https://git.kernel.org/stable/c/f35e3b5784221654f9cdbd6222275a7fa203f6c3"
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      ],
      "title": "futex: Fix private hash use-after-free on resize",
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  "cveMetadata": {
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-98788",
    "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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  "dataVersion": "5.2",
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      "date": "2026-11-02",
      "epss": "0.00155",
      "percentile": "0.04659"
    },
    "microsoft_vex": {
      "current_release_date": "2026-10-21T18:40:07.000Z",
      "cve": "CVE-2026-98788",
      "id": "msrc_CVE-2026-98788",
      "initial_release_date": "2026-10-20T22:24:08.000Z",
      "product_status:under_investigation": "1",
      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "futex: Fix private hash use-after-free on resize",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-98788.json",
      "version": "2"
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                    "versionType": "git"
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        ],
        "cveTags": [],
        "descriptions": [
          {
            "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."
          }
        ],
        "id": "CVE-2026-98788",
        "lastModified": "2026-10-19T10:19:42.873",
        "metrics": {},
        "published": "2026-10-18T16:17:32.787",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/5d5dc18b3a9ac011619b7d3af4514bf9e9b6a6af"
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            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/f35e3b5784221654f9cdbd6222275a7fa203f6c3"
          }
        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-10-21T14:59:42+00:00",
      "cve": "CVE-2026-98788",
      "id": "CVE-2026-98788",
      "initial_release_date": "2026-10-18T15:48:24.833000+00:00",
      "product_status:known_affected": "77",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: kernel: Privilege escalation via use-after-free during futex hash resizing",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-98788.json",
      "version": "3"
    }
  }
}



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