CVE-2026-98281 (GCVE-0-2026-98281)
Vulnerability from cvelistv5
Published
2026-10-06 08:45
Modified
2026-10-19 09:16
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: futex: Also allocate private hash on vfork() As Jann demonstrated, it is entirely feasible to access the mm through vfork(). Therefore we need to allocate a private hash on vfork() as well as any other CLONE_VM user. Specifically, it must be avoided to have (private) futex waiters before allocating the private hash.
References
Impacted products
Vendor Product Version
Linux Linux Version: 1dcd36420af2da5bd59306dba9caf78e3d248b1d
Version: ee9dce44362b2d8132c32964656ab6dff7dfbc6a
Version: ee9dce44362b2d8132c32964656ab6dff7dfbc6a
Version: 974ac49a9a068b0591a59f65c63eb06579a13091
Version: 6.18.33   ≤
Version: 7.0.10   ≤
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
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          "vendor": "Linux",
          "versions": [
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              "status": "unaffected",
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              "versionType": "original_commit_for_fix"
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          "nodes": [
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              "cpeMatch": [
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                  "versionStartIncluding": "6.18.33",
                  "vulnerable": true
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                {
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                  "vulnerable": true
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              ],
              "negate": false,
              "operator": "OR"
            }
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        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nfutex: Also allocate private hash on vfork()\n\nAs Jann demonstrated, it is entirely feasible to access the mm through vfork().\nTherefore we need to allocate a private hash on vfork() as well as any other\nCLONE_VM user.\n\nSpecifically, it must be avoided to have (private) futex waiters before\nallocating the private hash."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The trigger is a local process calling vfork()/clone3(CLONE_VM|CLONE_VFORK) in kernel_clone()/copy_process(), where need_futex_hash_allocate_default() skipped the private hash, followed by futex() syscalls on the shared mm. No remote peer supplies any input.\nAC:L - The attacker owns every task involved: the vfork parent (killed through its TASK_KILLABLE wait_for_vfork_done, so its futex exit path runs on the shared mm) and the vfork child, which creates a thread to publish the first private hash. Both sides of the race are under attacker control, so it can be retried at will.\nPR:L - vfork, clone, futex(FUTEX_WAIT/LOCK_PI), robust lists and kill() all work for an ordinary unprivileged user with no capability checks. The hash allocation in futex_hash_allocate_default() has no privilege gate either.\nUI:N - The attacker\u0027s own processes create the shared-mm state and the futex operations. No other user has to do anything.\nS:U - The damaged objects are kernel futex state (mm-\u003efutex.phash, hash buckets, pi_state) inside the same kernel security authority. No guest/host or IOMMU boundary is crossed.\nC:H - __futex_pivot_hash() leaves waiters queued in the global hash when the private hash is first published, so later PI/requeue operations take a different bucket lock. Futex PI state handled under two different bucket locks is the classic futex use-after-free pattern, and the earlier bug from this same assumption was a KASAN use-after-free, so kernel memory disclosure is plausible.\nI:H - A freed pi_state or private-hash reference that the attacker can reallocate gives a kernel heap write primitive, as in earlier futex PI use-after-free exploits, so local privilege escalation is possible.\nA:H - Waiters stranded in the global hash miss every later wake that goes to the private bucket, which hangs the affected tasks. The pi_state/reference corruption from inconsistent bucket locking can cause a KASAN splat or kernel oops."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T09:16:52.791Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/5468a4855b63b30156a79e5248e01bf1a2c18dd7"
        },
        {
          "url": "https://git.kernel.org/stable/c/eecbafa8cabbc4d1482f6a5e2acc25a8f934681b"
        },
        {
          "url": "https://git.kernel.org/stable/c/b61b6f95d6722ddbbbd09e689fa41b55fd36f9a5"
        }
      ],
      "title": "futex: Also allocate private hash on vfork()",
      "x_generator": {
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      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-98281",
    "datePublished": "2026-10-06T08:45:40.719Z",
    "dateReserved": "2026-09-25T10:25:14.335Z",
    "dateUpdated": "2026-10-19T09:16:52.791Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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