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

Vulnerability from cvelistv5 – Published: 2026-09-16 10:32 – Updated: 2026-10-19 08:54
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
Linux CNA under the mitre root
CNA scorecard D 53/100 over 7018 records in the last 180 days details
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)
guessed Create a notification for this product.
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 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
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{
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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."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T08:54:58.219Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
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          "url": "https://git.kernel.org/stable/c/053f2068cf9b0654b651fed5ad7649d3deb982bf"
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          "url": "https://git.kernel.org/stable/c/6c996b12bbe4a6023076e8eee3cfaf2cc99db76c"
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    "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"
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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": "2026-10-19T09:18:37.817",
        "metrics": {},
        "published": "2026-09-16T11:17:01.397",
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        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Low",
      "current_release_date": "2026-10-05T20:02:23+00:00",
      "cve": "CVE-2026-89923",
      "id": "CVE-2026-89923",
      "initial_release_date": "2026-09-16T00:00:00+00:00",
      "product_status:known_affected": "249",
      "product_status:known_not_affected": "28",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: KVM: s390: Free guest debug data on vcpu destroy",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89923.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "low",
      "current_release_date": "2026-10-20T00:54:52Z",
      "cve": "CVE-2026-89923",
      "id": "CVE-2026-89923",
      "initial_release_date": "2026-09-17T16:34:41Z",
      "product_status:known_affected": "344",
      "product_status:known_not_affected": "4",
      "product_status:recommended": "4",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-89923",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/2026/cve-2026-89923.json",
      "version": "5"
    }
  }
}



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  • 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.
Vulnerability timeline

Sightings and recorded dates, grouped by day · UTC

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How durations are calculated

Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.

Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.

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