{
  "schema_version": "1.6.1",
  "id": "RPI-CVE-2026-52973",
  "modified": "2026-10-09T11:39:44Z",
  "upstream": [
    "CVE-2026-52973"
  ],
  "published": "2026-06-24T16:31:02Z",
  "summary": "futex: Drop CLONE_THREAD requirement for private default hash alloc",
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nfutex: Drop CLONE_THREAD requirement for private default hash alloc\n\nCurrently need_futex_hash_allocate_default() depends on strict pthread\nsemantics, abusing CLONE_THREAD.  This breaks the non-concurrency\nassumptions when doing the mm->futex_ref pcpu allocations, leading to\nbugs[0] when sharing the mm in other ways; ie:\n\n    BUG: KASAN: slab-use-after-free in futex_hash_put\n\n... where the +1 bias can end up on a percpu counter that mm->futex_ref\nno longer points at.\n\nLoosen the check to cover any CLONE_VM clone, except vfork().  Excluding\nvfork keeps the existing paths untouched (no overhead), and we can't\nrace in the first place: either the parent is suspended and the child\nruns alone, or mm->futex_ref is already allocated from an earlier\nCLONE_VM.",
  "severity": [
    {
      "type": "CVSS_V3",
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
    }
  ],
  "affected": [
    {
      "package": {
        "ecosystem": "Raspberry Pi OS:13",
        "name": "linux"
      },
      "versions": [
        "1:6.18.29-1+rpt1"
      ],
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "linux-image-6.18.29+rpt-rpi-2712",
            "binary_version": "1:6.18.29-1+rpt1"
          },
          {
            "binary_name": "linux-image-6.18.29+rpt-rpi-v6",
            "binary_version": "1:6.18.29-1+rpt1"
          },
          {
            "binary_name": "linux-image-6.18.29+rpt-rpi-v7",
            "binary_version": "1:6.18.29-1+rpt1"
          },
          {
            "binary_name": "linux-image-6.18.29+rpt-rpi-v8",
            "binary_version": "1:6.18.29-1+rpt1"
          },
          {
            "binary_name": "linux-image-6.18.29+rpt-rpi-v8-rt",
            "binary_version": "1:6.18.29-1+rpt1"
          }
        ]
      },
      "database_specific": {
        "per_version": {
          "1:6.18.29-1+rpt1": {
            "linux_commit": "66318c5b5cd8145a662303af12ed39ac07eb27cc",
            "upstream_version": "6.18.29",
            "assessment": "commit ancestry (strak rule)",
            "upstream_fixed": "6.18.33"
          }
        }
      }
    }
  ],
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-52973"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/1dcd36420af2da5bd59306dba9caf78e3d248b1d"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/974ac49a9a068b0591a59f65c63eb06579a13091"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/ee9dce44362b2d8132c32964656ab6dff7dfbc6a"
    }
  ],
  "database_specific": {
    "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git",
    "upstream_modified": "2026-08-05T13:16:28Z",
    "severity": {
      "source": "kernel CNA",
      "cvss_v3_score": 7.8,
      "cvss_v3_severity": "High",
      "scenario": "AV:L - The vulnerable path is reached through local `clone`/`clone3`, `prctl(PR_FUTEX_HASH, ...)`, and futex syscalls on user memory. It is not reachable directly over a network or adjacent/physical interface.\nAC:L - The race is attacker-controlled: an unprivileged process can create multiple `CLONE_VM` non-`CLONE_THREAD` siblings and issue concurrent private futex hash operations. The public report demonstrates a reproducible unprivileged KASAN UAF using attacker-controlled timing aids.\nPR:L - The trigger uses ordinary unprivileged local syscalls and the report reproduced it as UID 1000 without capabilities. No real root or init-namespace administrative privilege is required.\nUI:N - No victim action is needed after the attacker can execute local code. The attacker controls the clone, prctl, userfaultfd, and futex operations.\nS:U - The corruption occurs within the Linux kernel due to local syscall handling and affects the same kernel security authority. There is no hypervisor, IOMMU, or separate-scope boundary crossing.\nC:H - This is a kernel use-after-free of a live `struct futex_private_hash`/bucket array, and UAF memory corruption can reasonably be leveraged for kernel memory disclosure. When uncertain, the higher-severity impact is appropriate.\nI:H - The UAF leaves futex code operating on freed and potentially attacker-reclaimed kernel heap memory, which can plausibly provide write/control-flow primitives. Kernel UAF memory corruption is scored as high integrity impact.\nA:H - The reported impact includes a KASAN slab-use-after-free in `futex_hash_put()` and can crash/oops the kernel. A repeatable local kernel crash is high availability impact."
    }
  }
}