CVE-2023-53205 (GCVE-0-2023-53205)

Vulnerability from cvelistv5 – Published: 2025-09-15 14:21 – Updated: 2026-10-15 21:41
VLAI
Title
KVM: s390/diag: fix racy access of physical cpu number in diag 9c handler
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.
Severity
7.3 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:N/A:H
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-10-15 21:34 UTC
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 6641 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 87e28a15c42cc592009c32a8c20e5789059027c2 , < a9ccf140a2a03a0ae82be4bdfbdd17bdaea72ff5 (git)
Affected: 87e28a15c42cc592009c32a8c20e5789059027c2 , < 86bfb18bad60fc468e5f112cbbd918462a8dd435 (git)
Affected: 87e28a15c42cc592009c32a8c20e5789059027c2 , < dc7e0192c470a53d847c79a2796f9ac429477a26 (git)
Affected: 87e28a15c42cc592009c32a8c20e5789059027c2 , < 0bc380beb78aa352eadbc21d934dd9606fcee808 (git)
guessed Create a notification for this product.
Linux Linux Affected: 5.13
Unaffected: 0 , < 5.13 (semver)
Unaffected: 5.15.121 , ≤ 5.15.* (semver)
Unaffected: 6.1.39 , ≤ 6.1.* (semver)
Unaffected: 6.4.4 , ≤ 6.4.* (semver)
Unaffected: 6.5 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
Show details on NVD website
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                  "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": "2026-10-15T21:41:27.937Z",
        "state": "PUBLISHED"
      },
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



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Sightings

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Nomenclature

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Vulnerability timeline

Sightings and recorded dates, grouped by day · UTC

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