CVE-2026-89923 (GCVE-0-2026-89923)

Vulnerability from cvelistv5 – Published: 2026-09-16 10:32 – Updated: 2026-09-16 10:32
VLAI
Title
KVM: s390: Free guest debug data on vcpu destroy
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.
Severity
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 27291e2165b6de70c476b7b675308113edd69a60 , < 053f2068cf9b0654b651fed5ad7649d3deb982bf (git)
Affected: 27291e2165b6de70c476b7b675308113edd69a60 , < 6c996b12bbe4a6023076e8eee3cfaf2cc99db76c (git)
Affected: 27291e2165b6de70c476b7b675308113edd69a60 , < d6280fc540d8f4653c9b54a78cb747e128070f5e (git)
Affected: 27291e2165b6de70c476b7b675308113edd69a60 , < 544a5a665019cef394ce8bda97fa7a2cab253781 (git)
Affected: 27291e2165b6de70c476b7b675308113edd69a60 , < 9a32c4c6a6c23b7f5bf765eb5b83ba7f64a8ec63 (git)
Affected: 27291e2165b6de70c476b7b675308113edd69a60 , < b5acacfdb8966abff91836c1c5bd7da59d8a526e (git)
Affected: 27291e2165b6de70c476b7b675308113edd69a60 , < e4d8b7f176b976474e0800ba71ee2dfa3ce263c9 (git)
Affected: 27291e2165b6de70c476b7b675308113edd69a60 , < e7f698b09d4a7c36b299acf680fc50fe868e2bcd (git)
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Linux Linux Affected: 3.16
Unaffected: 0 , < 3.16 (semver)
Unaffected: 5.10.270 , ≤ 5.10.* (semver)
Unaffected: 5.15.221 , ≤ 5.15.* (semver)
Unaffected: 6.1.188 , ≤ 6.1.* (semver)
Unaffected: 6.6.157 , ≤ 6.6.* (semver)
Unaffected: 6.12.110 , ≤ 6.12.* (semver)
Unaffected: 6.18.51 , ≤ 6.18.* (semver)
Unaffected: 7.2.5 , ≤ 7.2.* (semver)
Unaffected: 7.3-rc1 , ≤ * (original_commit_for_fix)
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{
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              "negate": false,
              "operator": "OR"
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        {
          "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": "2026-09-16T10:32:16.765Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
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          "url": "https://git.kernel.org/stable/c/053f2068cf9b0654b651fed5ad7649d3deb982bf"
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        {
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    "datePublished": "2026-09-16T10:32:16.765Z",
    "dateReserved": "2026-09-11T19:38:34.775Z",
    "dateUpdated": "2026-09-16T10:32:16.765Z",
    "state": "PUBLISHED"
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      "source": "Microsoft CSAF VEX",
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            "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."
          }
        ],
        "id": "CVE-2026-89923",
        "lastModified": "2026-09-16T11:17:01.397",
        "metrics": {},
        "published": "2026-09-16T11:17:01.397",
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        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
      }
    },
    "suse_vex": {
      "aggregate_severity": "low",
      "current_release_date": "2026-09-19T01:42:48Z",
      "cve": "CVE-2026-89923",
      "id": "CVE-2026-89923",
      "initial_release_date": "2026-09-17T16:34:41Z",
      "product_status:known_affected": "343",
      "product_status:known_not_affected": "4",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-89923",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-89923.json",
      "version": "3"
    }
  }
}



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