CVE-2023-53205 (GCVE-0-2023-53205)
Vulnerability from cvelistv5 – Published: 2025-09-15 14:21 – Updated: 2026-08-05 09:13
VLAI
EPSS
VEX
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)
Assigner
References
Impacted products
2 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 | |
| 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 |
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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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"status": "final",
"title": "kernel: KVM: s390/diag: fix racy access of physical cpu number in diag 9c handler",
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
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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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.
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