Vulnerability-Lookup

GHSA-9R2V-25MX-G9GJ

Vulnerability from github – Published: 2025-09-15 15:31 – Updated: 2025-12-04 15:30

Details

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

7.8 (High)


                  
                    CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

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{
  "affected": [],
  "aliases": [
    "CVE-2023-53205"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-787"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2025-09-15T15:15:46Z",
    "severity": "HIGH"
  },
  "details": "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.",
  "id": "GHSA-9r2v-25mx-g9gj",
  "modified": "2025-12-04T15:30:31Z",
  "published": "2025-09-15T15:31:28Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2023-53205"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/0bc380beb78aa352eadbc21d934dd9606fcee808"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/86bfb18bad60fc468e5f112cbbd918462a8dd435"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/a9ccf140a2a03a0ae82be4bdfbdd17bdaea72ff5"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/dc7e0192c470a53d847c79a2796f9ac429477a26"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}

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

Vulnerability from cvelistv5 – Published: 2025-09-15 14:21 – Updated: 2026-10-15 21:41

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 6820 records in the last 180 days details

References

4 references

URL	Tags
https://git.kernel.org/stable/c/a9ccf140a2a03a0ae…
https://git.kernel.org/stable/c/86bfb18bad60fc468…
https://git.kernel.org/stable/c/dc7e0192c470a53d8…
https://git.kernel.org/stable/c/0bc380beb78aa352e…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 87e28a15c42cc592009c32a8c20e5789059027c2 , < a9ccf140a2a03a0ae82be4bdfbdd17bdaea72ff5 (git) Affected: 87e28a15c42cc592009c32a8c20e5789059027c2 , < 86bfb18bad60fc468e5f112cbbd918462a8dd435 (git) Affected: 87e28a15c42cc592009c32a8c20e5789059027c2 , < dc7e0192c470a53d847c79a2796f9ac429477a26 (git) Affected: 87e28a15c42cc592009c32a8c20e5789059027c2 , < 0bc380beb78aa352eadbc21d934dd9606fcee808 (git)
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)

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                "id": "CVE-2023-53205",
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              "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."
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Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

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