{
  "schema_version": "1.6.1",
  "id": "RPI-CVE-2025-21836",
  "modified": "2026-10-09T11:39:44Z",
  "upstream": [
    "CVE-2025-21836"
  ],
  "published": "2025-03-07T09:10:23Z",
  "summary": "io_uring/kbuf: reallocate buf lists on upgrade",
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nio_uring/kbuf: reallocate buf lists on upgrade\n\nIORING_REGISTER_PBUF_RING can reuse an old struct io_buffer_list if it\nwas created for legacy selected buffer and has been emptied. It violates\nthe requirement that most of the field should stay stable after publish.\nAlways reallocate it instead.",
  "severity": [
    {
      "type": "CVSS_V3",
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
    }
  ],
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  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.cve.org/CVERecord?id=CVE-2025-21836"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/146a185f6c05ee263db715f860620606303c4633"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/7d0dc28dae836caf7645fef62a10befc624dd17b"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/2a5febbef40ce968e295a7aeaa5d5cbd9e3e5ad4"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/8802766324e1f5d414a81ac43365c20142e85603"
    }
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  "database_specific": {
    "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git",
    "upstream_modified": "2026-08-05T12:19:11Z",
    "severity": {
      "source": "kernel CNA",
      "cvss_v3_score": 7.8,
      "cvss_v3_severity": "High",
      "scenario": "AV:L - The vulnerable code is reached only through the io_uring_setup/io_uring_register syscalls; there is no network or adjacent path, so exploitation requires local access to issue syscalls.\nAC:L - The attacker performs every step themselves (create a legacy buffer group, empty it, upgrade the same bgid via PBUF_RING, then mmap), controlling both sides of any race; the trigger is fully deterministic and reliable.\nPR:L - io_uring is available to unprivileged users by default (kernel.io_uring_disabled=0) and provided-buffer registration needs no capability, so only a basic local user account is required.\nUI:N - The entire sequence is driven by the attacking process; no action by any other user or victim is needed.\nS:U - The corruption is confined to the kernel's own security authority (standard local privilege escalation) and does not cross a VM, IOMMU, or sandbox boundary.\nC:H - The type confusion / use-after-free of the io_buffer_list and the retained user mapping to freed kernel pages give the attacker read access to reallocated kernel memory, enabling arbitrary kernel information disclosure.\nI:H - The same UAF and shared-page primitive give write access to freed/reallocated kernel memory, exploitable for arbitrary kernel write and privilege escalation as demonstrated for this io_uring buffer-ring bug class.\nA:H - At minimum the type confusion and use-after-free corrupt kernel structures, causing an oops/panic and denial of service."
    }
  }
}