{"id":"CVE-2023-53205","state":"PUBLISHED","title":"KVM: s390/diag: fix racy access of physical cpu number in diag 9c handler","description":"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.","publishedAt":"2025-09-15T14:21:33.560Z","updatedAt":"2026-10-15T21:41:27.937Z","severity":{"score":7.3,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:N/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"87e28a15c42cc592009c32a8c20e5789059027c2","status":"affected","lessThan":"a9ccf140a2a03a0ae82be4bdfbdd17bdaea72ff5","versionType":"git"},{"version":"87e28a15c42cc592009c32a8c20e5789059027c2","status":"affected","lessThan":"86bfb18bad60fc468e5f112cbbd918462a8dd435","versionType":"git"},{"version":"87e28a15c42cc592009c32a8c20e5789059027c2","status":"affected","lessThan":"dc7e0192c470a53d847c79a2796f9ac429477a26","versionType":"git"},{"version":"87e28a15c42cc592009c32a8c20e5789059027c2","status":"affected","lessThan":"0bc380beb78aa352eadbc21d934dd9606fcee808","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["arch/s390/kvm/diag.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.13","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.13","versionType":"semver"},{"version":"5.15.121","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.39","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.4.4","status":"unaffected","lessThanOrEqual":"6.4.*","versionType":"semver"},{"version":"6.5","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["arch/s390/kvm/diag.c"]}],"references":["https://git.kernel.org/stable/c/a9ccf140a2a03a0ae82be4bdfbdd17bdaea72ff5","https://git.kernel.org/stable/c/86bfb18bad60fc468e5f112cbbd918462a8dd435","https://git.kernel.org/stable/c/dc7e0192c470a53d847c79a2796f9ac429477a26","https://git.kernel.org/stable/c/0bc380beb78aa352eadbc21d934dd9606fcee808"],"weaknesses":[],"ingestedAt":"2026-10-29T20:06:33.064Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2023/53xxx/CVE-2023-53205.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2023-53205","state":"PUBLISHED","datePublished":"2025-09-15T14:21:33.560Z","dateUpdated":"2026-10-15T21:41:27.937Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2025-09-15T13:59:19.068Z"},"containers":{"cna":{"title":"KVM: s390/diag: fix racy access of physical cpu number in diag 9c handler","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."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"87e28a15c42cc592009c32a8c20e5789059027c2","status":"affected","lessThan":"a9ccf140a2a03a0ae82be4bdfbdd17bdaea72ff5","versionType":"git"},{"version":"87e28a15c42cc592009c32a8c20e5789059027c2","status":"affected","lessThan":"86bfb18bad60fc468e5f112cbbd918462a8dd435","versionType":"git"},{"version":"87e28a15c42cc592009c32a8c20e5789059027c2","status":"affected","lessThan":"dc7e0192c470a53d847c79a2796f9ac429477a26","versionType":"git"},{"version":"87e28a15c42cc592009c32a8c20e5789059027c2","status":"affected","lessThan":"0bc380beb78aa352eadbc21d934dd9606fcee808","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["arch/s390/kvm/diag.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.13","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.13","versionType":"semver"},{"version":"5.15.121","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.39","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.4.4","status":"unaffected","lessThanOrEqual":"6.4.*","versionType":"semver"},{"version":"6.5","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["arch/s390/kvm/diag.c"]}],"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"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:N/A:H","baseScore":7.3,"baseSeverity":"HIGH"},"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 → __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->cpu 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’s 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":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T09:13:05.376Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.13","versionEndExcluding":"5.15.121"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.13","versionEndExcluding":"6.1.39"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.13","versionEndExcluding":"6.4.4"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.13","versionEndExcluding":"6.5"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2023-53205","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"version":"2.0.3","timestamp":"2026-10-15T21:34:27.370447Z"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-15T21:41:27.937Z"}}]}}}