KVM: x86: Ignore -EBUSY when checking nested events from vcpu_block()

{
  "id": "e32cd03cf624165b257226f98028dda8d5c8500d3c9f85c094fe954c757a7f3b",
  "url": "https://osv.dev/vulnerability/CVE-2026-43265",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "KVM: x86: Ignore -EBUSY when checking nested events from vcpu_block()",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: KVM: x86: Ignore -EBUSY when checking nested events from vcpu_block() Ignore -EBUSY when checking nested events after exiting a blocking state while L2 is active, as exiting to userspace will generate a spurious userspace exit, usually with KVM_EXIT_UNKNOWN, and likely lead to the VM's demise. Continuing with the wakeup isn't perfect either, as *something* has gone sideways if a vCPU is awakened in L2 with an injected event (or worse, a nested run pending), but continuing on gives the VM a decent chance of surviving without any major side effects. As explained in the Fixes commits, it _should_ be impossible for a vCPU to be put into a blocking state with an already-injected event (exception, IRQ, or NMI). Unfortunately, userspace can stuff MP_STATE and/or injected events, and thus put the vCPU into what should be an impossible state. Don't bother trying to preserve the WARN, e.g. with an anti-syzkaller Kconfig, as WARNs can (hopefully) be added in paths where _KVM_ would be violating x86 architecture, e.g. by WARNing if KVM attempts to inject an exception or interrupt while the vCPU isn't running.",
    "evidence": "osv:CVE-2026-43265",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.1.167",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.6.130",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.12.77",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.17",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.19.6",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-43265",
      "aliases": [
        "CVE-2026-43265"
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
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                  "introduced": "26844fee6adee9b1557d2279b0506285de9ee82b"
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                {
                  "fixed": "78265cd066d73a5cb41c088fcae4a2515e480d97"
                },
                {
                  "fixed": "ec3be7dc9391085a2d96700e159d66d1328b7ff6"
                },
                {
                  "fixed": "2657439265d34a911886b916ba8be97ecc117d51"
                },
                {
                  "fixed": "1e88b5f854bdb469424132e0bb44793ad7a7c20a"
                },
                {
                  "fixed": "1c957773063ed3264953597e32990a748381caf6"
                },
                {
                  "fixed": "ead63640d4e72e6f6d464f4e31f7fecb79af8869"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-43265.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.1.0"
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                {
                  "fixed": "6.1.167"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.2.0"
                },
                {
                  "fixed": "6.6.130"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.7.0"
                },
                {
                  "fixed": "6.12.77"
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              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.13.0"
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                {
                  "fixed": "6.18.17"
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              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.19.0"
                },
                {
                  "fixed": "6.19.6"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-43265.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:42.497060519Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/1c957773063ed3264953597e32990a748381caf6",
        "https://git.kernel.org/stable/c/1e88b5f854bdb469424132e0bb44793ad7a7c20a",
        "https://git.kernel.org/stable/c/2657439265d34a911886b916ba8be97ecc117d51",
        "https://git.kernel.org/stable/c/78265cd066d73a5cb41c088fcae4a2515e480d97",
        "https://git.kernel.org/stable/c/ead63640d4e72e6f6d464f4e31f7fecb79af8869",
        "https://git.kernel.org/stable/c/ec3be7dc9391085a2d96700e159d66d1328b7ff6",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/43xxx/CVE-2026-43265.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-43265",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/43xxx/CVE-2026-43265.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-43265",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 510217,
  "published_at": "2026-05-06T11:28:51.552+00:00"
}