CVE-2026-80929 (GCVE-0-2026-80929)
Vulnerability from cvelistv5
Published
2026-09-11 19:42
Modified
2026-10-19 08:45
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: sysctl: move the "cad_pid" entry from pid_table[] to kern_reboot_table[] cad_pid is global, and kill_cad_pid() is only used in the root namespace. However, due to pid_table_root_permissions(), a non-root user can unshare pid/user namespaces and modify it from the child namespace. This makes no sense and is simply wrong. Move it to kern_reboot_table[] where it logically belongs; this ensures that only GLOBAL_ROOT_UID can read/modify this sysctl. Note that this patch doesn't preserve "#ifdef CONFIG_PROC_SYSCTL" around the "cad_pid"; CONFIG_PROC_SYSCTL selects CONFIG_SYSCTL, so it is always set when kern_reboot_table[] is compiled.
References
Impacted products
Vendor Product Version
Linux Linux Version: e054bcbe7e7af2baad3752f1a4916a7fffc0457e
Version: e054bcbe7e7af2baad3752f1a4916a7fffc0457e
Version: e054bcbe7e7af2baad3752f1a4916a7fffc0457e
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "kernel/pid.c",
            "kernel/reboot.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "status": "affected",
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              "versionType": "git"
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              "status": "affected",
              "version": "e054bcbe7e7af2baad3752f1a4916a7fffc0457e",
              "versionType": "git"
            },
            {
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              "status": "affected",
              "version": "e054bcbe7e7af2baad3752f1a4916a7fffc0457e",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "kernel/pid.c",
            "kernel/reboot.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.17"
            },
            {
              "lessThan": "6.17",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.50",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.4",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.50",
                  "versionStartIncluding": "6.17",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.4",
                  "versionStartIncluding": "6.17",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3",
                  "versionStartIncluding": "6.17",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsysctl: move the \"cad_pid\" entry from pid_table[] to kern_reboot_table[]\n\ncad_pid is global, and kill_cad_pid() is only used in the root namespace.\n\nHowever, due to pid_table_root_permissions(), a non-root user can unshare\npid/user namespaces and modify it from the child namespace. This makes no\nsense and is simply wrong.\n\nMove it to kern_reboot_table[] where it logically belongs; this ensures\nthat only GLOBAL_ROOT_UID can read/modify this sysctl.\n\nNote that this patch doesn\u0027t preserve \"#ifdef CONFIG_PROC_SYSCTL\" around\nthe \"cad_pid\"; CONFIG_PROC_SYSCTL selects CONFIG_SYSCTL, so it is always\nset when kern_reboot_table[] is compiled."
        }
      ],
      "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 - Unprivileged local processes reach proc_do_cad_pid() by opening and writing /proc/sys/kernel/cad_pid after creating user and PID namespaces; this is a procfs sysctl syscall path, not a network, adjacent-wireless, or physical-device handler.\nAC:L - The attacker fully controls namespace creation and concurrent sysctl reads/writes of the shared global cad_pid pointer, so the proc_do_cad_pid() use-after-free race does not depend on victim state, rare configs, or other conditions outside attacker influence.\nPR:L - pid_table_root_permissions() treats CAP_SYS_ADMIN or uid 0 in the PID namespace\u0027s user namespace as owner of the 0600 cad_pid sysctl, which an unprivileged user obtains by unsharing user and PID namespaces rather than needing init-namespace root.\nUI:N - The attacker triggers the flaw entirely through their own unshare, proc mount, and read/write of kernel.cad_pid; no other user must press Ctrl-Alt-Del, mount a filesystem, or take any action.\nS:U - Successful exploitation corrupts host kernel memory and hijacks the global cad_pid used by kill_cad_pid(); this remains inside the kernel\u0027s security authority and is not a VM, IOMMU, or DMA boundary bypass.\nC:H - Racing a cad_pid sysctl write (put_pid of the last reference) against a sysctl read use-after-frees struct pid in pid_vnr()/pid_nr_ns(), which per kernel CVSS guidance provides an arbitrary kernel-read primitive via slab reuse.\nI:H - The same use-after-free of struct pid is exploitable for heap spraying and control-flow hijack of kernel PID/signal paths, and the write also replaces host-global cad_pid so privileged kernel SIGINT/SIGPWR are redirected away from init.\nA:H - The use-after-free produces a kernel oops or panic on the pid_nr_ns() dereference of freed memory, as shown by the KASAN report; replacing cad_pid also persistently breaks host Ctrl-Alt-Del and power-button delivery to init."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T08:45:13.127Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/e8527de7fea191fda704792a56081f9009aeec37"
        },
        {
          "url": "https://git.kernel.org/stable/c/a09bc4eaa67e1a72df3b6d0beb3afeef1e1fdfcd"
        },
        {
          "url": "https://git.kernel.org/stable/c/7170ca01623b399c97f2ae9d3e228badc1f25ea3"
        }
      ],
      "title": "sysctl: move the \"cad_pid\" entry from pid_table[] to kern_reboot_table[]",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-80929",
    "datePublished": "2026-09-11T19:42:04.778Z",
    "dateReserved": "2026-08-26T14:34:25.802Z",
    "dateUpdated": "2026-10-19T08:45:13.127Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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