CVE-2023-53205 (GCVE-0-2023-53205)
Vulnerability from cvelistv5
Published
2025-09-15 14:21
Modified
2026-08-05 09:13
Severity ?
7.3 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:N/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: KVM: s390/diag: fix racy access of physical cpu number in diag 9c handler We do check for target CPU == -1, but this might change at the time we are going to use it. Hold the physical target CPU in a local variable to avoid out-of-bound accesses to the cpu arrays.
References
Impacted products
Vendor Product Version
Linux Linux Version: 87e28a15c42cc592009c32a8c20e5789059027c2
Version: 87e28a15c42cc592009c32a8c20e5789059027c2
Version: 87e28a15c42cc592009c32a8c20e5789059027c2
Version: 87e28a15c42cc592009c32a8c20e5789059027c2
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "arch/s390/kvm/diag.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "lessThan": "a9ccf140a2a03a0ae82be4bdfbdd17bdaea72ff5",
              "status": "affected",
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              "versionType": "git"
            },
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              "versionType": "git"
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              "status": "affected",
              "version": "87e28a15c42cc592009c32a8c20e5789059027c2",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "arch/s390/kvm/diag.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "5.13"
            },
            {
              "lessThan": "5.13",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.121",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.39",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.4.*",
              "status": "unaffected",
              "version": "6.4.4",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "6.5",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.15.121",
                  "versionStartIncluding": "5.13",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.1.39",
                  "versionStartIncluding": "5.13",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.4.4",
                  "versionStartIncluding": "5.13",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.5",
                  "versionStartIncluding": "5.13",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: s390/diag: fix racy access of physical cpu number in diag 9c handler\n\nWe do check for target CPU == -1, but this might change at the time we\nare going to use it. Hold the physical target CPU in a local variable to\navoid out-of-bound accesses to the cpu arrays."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.3,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:N/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The bug is reached when a KVM guest on s390 executes privileged DIAG 0x9c, which exits via SIE intercept into kvm_s390_handle_diag \u2192 __diag_time_slice_end_directed on the host; there is no network or adjacent-link entry point.\nAC:L - A multi-vCPU guest attacker controls both sides of the race (spam DIAG 9c from one vCPU while forcing the target vCPU through kvm_arch_vcpu_put so tcpu-\u003ecpu becomes -1) and can retry freely; scoring assumes the worst reasonable deployment with diag9c_forwarding_hz enabled so the forwarding path is live.\nPR:L - Triggering requires only the ability to run a KVM guest (/dev/kvm kvm-group/VMM user or cloud tenant) and issue DIAG from guest supervisor state; that is ordinary unprivileged-vs-host access, not real init-namespace root.\nUI:N - The attacker drives the DIAG 9c spam and target-vCPU scheduling from their own guest with no separate victim action required.\nS:C - A guest-triggered host bug that indexes host kernel cpu arrays (lowcore_ptr/pcpu_devices) crosses the guest/host virtualization boundary and can crash or touch host kernel state outside the guest\u2019s security authority.\nC:L - Winning the race yields a fixed negative-index (-1) out-of-bounds read of host lowcore_ptr/pcpu_devices and a subsequent pointer chase; this is a bounded adjacent host-kernel read without a guest-visible bulk disclosure path, matching C:L rather than C:N or C:H.\nI:N - The vulnerable path only reads OOB array state and may issue a spurious host DIAG 9c yield; there is no out-of-bounds write, UAF store, or other host integrity/control-flow primitive.\nA:H - Dereferencing lowcore_ptr[-1] (often NULL/garbage) or using an invalid pcpu_devices[-1] address can oops/panic the host kernel, so availability impact is High and repeatable whenever the race is won."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T09:13:05.376Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/a9ccf140a2a03a0ae82be4bdfbdd17bdaea72ff5"
        },
        {
          "url": "https://git.kernel.org/stable/c/86bfb18bad60fc468e5f112cbbd918462a8dd435"
        },
        {
          "url": "https://git.kernel.org/stable/c/dc7e0192c470a53d847c79a2796f9ac429477a26"
        },
        {
          "url": "https://git.kernel.org/stable/c/0bc380beb78aa352eadbc21d934dd9606fcee808"
        }
      ],
      "title": "KVM: s390/diag: fix racy access of physical cpu number in diag 9c handler",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2023-53205",
    "datePublished": "2025-09-15T14:21:33.560Z",
    "dateReserved": "2025-09-15T13:59:19.068Z",
    "dateUpdated": "2026-08-05T09:13:05.376Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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