CVE-2026-89923 (GCVE-0-2026-89923)
Vulnerability from cvelistv5
Published
2026-09-16 10:32
Modified
2026-10-19 08:54
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: KVM: s390: Free guest debug data on vcpu destroy kvm_s390_clear_bp_data() is only called from kvm_arch_vcpu_ioctl_set_guest_debug(), i.e. when user space changes or disables debugging. A vCPU that is destroyed while hardware breakpoints are still armed - the normal case when the VMM just exits or crashes - leaks hw_bp_info, hw_wp_info and all old_data buffers, since generic KVM frees the vCPU right after kvm_arch_vcpu_destroy(). That is bounded by MAX_BP_COUNT entries, so roughly 8 KiB per vCPU, but it is unbounded over VM lifetimes. The allocations are GFP_KERNEL_ACCOUNT, so the charge also outlives the exiting process and pins dying memcgs. Fix by clearing the debug data on vCPU destruction. Calling it unconditionally is fine: struct kvm_vcpu is zero allocated, so for a vCPU that never enabled debugging the counters are 0 and the pointers NULL.
References
Impacted products
Vendor Product Version
Linux Linux Version: 27291e2165b6de70c476b7b675308113edd69a60
Version: 27291e2165b6de70c476b7b675308113edd69a60
Version: 27291e2165b6de70c476b7b675308113edd69a60
Version: 27291e2165b6de70c476b7b675308113edd69a60
Version: 27291e2165b6de70c476b7b675308113edd69a60
Version: 27291e2165b6de70c476b7b675308113edd69a60
Version: 27291e2165b6de70c476b7b675308113edd69a60
Version: 27291e2165b6de70c476b7b675308113edd69a60
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "arch/s390/kvm/kvm-s390.c"
          ],
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          "vendor": "Linux",
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          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "3.16"
            },
            {
              "lessThan": "3.16",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.10.*",
              "status": "unaffected",
              "version": "5.10.270",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.221",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.188",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.157",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.110",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.51",
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            },
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              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.5",
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            },
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              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                  "versionStartIncluding": "3.16",
                  "vulnerable": true
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                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: s390: Free guest debug data on vcpu destroy\n\nkvm_s390_clear_bp_data() is only called from\nkvm_arch_vcpu_ioctl_set_guest_debug(), i.e. when user space changes or\ndisables debugging. A vCPU that is destroyed while hardware breakpoints\nare still armed - the normal case when the VMM just exits or crashes -\nleaks hw_bp_info, hw_wp_info and all old_data buffers, since generic KVM\nfrees the vCPU right after kvm_arch_vcpu_destroy().\n\nThat is bounded by MAX_BP_COUNT entries, so roughly 8 KiB per vCPU, but\nit is unbounded over VM lifetimes. The allocations are\nGFP_KERNEL_ACCOUNT, so the charge also outlives the exiting process and\npins dying memcgs.\n\nFix by clearing the debug data on vCPU destruction. Calling it\nunconditionally is fine: struct kvm_vcpu is zero allocated, so for a vCPU\nthat never enabled debugging the counters are 0 and the pointers NULL."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T08:54:58.219Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/053f2068cf9b0654b651fed5ad7649d3deb982bf"
        },
        {
          "url": "https://git.kernel.org/stable/c/6c996b12bbe4a6023076e8eee3cfaf2cc99db76c"
        },
        {
          "url": "https://git.kernel.org/stable/c/d6280fc540d8f4653c9b54a78cb747e128070f5e"
        },
        {
          "url": "https://git.kernel.org/stable/c/544a5a665019cef394ce8bda97fa7a2cab253781"
        },
        {
          "url": "https://git.kernel.org/stable/c/9a32c4c6a6c23b7f5bf765eb5b83ba7f64a8ec63"
        },
        {
          "url": "https://git.kernel.org/stable/c/b5acacfdb8966abff91836c1c5bd7da59d8a526e"
        },
        {
          "url": "https://git.kernel.org/stable/c/e4d8b7f176b976474e0800ba71ee2dfa3ce263c9"
        },
        {
          "url": "https://git.kernel.org/stable/c/e7f698b09d4a7c36b299acf680fc50fe868e2bcd"
        }
      ],
      "title": "KVM: s390: Free guest debug data on vcpu destroy",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89923",
    "datePublished": "2026-09-16T10:32:16.765Z",
    "dateReserved": "2026-09-11T19:38:34.775Z",
    "dateUpdated": "2026-10-19T08:54:58.219Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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