MOKSHA-2026-0084

Vulnerability from moksha – Published: 2026-04-24 06:00 – Updated:
VLAI
Title
Firmware Type Denial of Service via VM.HVM_boot_params firmware
Summary
A vm-admin in XAPI-based hypervisors (XenServer, XCP-ng) can disrupt VM boot by writing an invalid value to VM.HVM_boot_params:firmware or removing the key. XAPI accepts any value at write time but validates at VM start (xapi_xenops.ml:255-268), raising Server_error on invalid values. Firmware key removal causes BIOS fallback, rendering UEFI guests unbootable. The impact is limited because vm-admin already has VM.hard_shutdown capability. The field has zero map_keys_roles entries.
Severity
3.1 (Low)
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
5.3 (Medium)
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
CWE
  • CWE-20 - Improper Input Validation
  • CWE-862 - Missing Authorization
References
Impacted products
Credits
Jakob Wolffhechel, Moksha
Show details on NVD website
To clipboard 

{
  "containers": {
    "cna": {
      "affected": [
        {
          "product": "XenServer",
          "vendor": "Cloud Software Group",
          "versions": [
            {
              "status": "affected",
              "version": "all",
              "versionType": "custom"
            }
          ]
        },
        {
          "product": "XCP-ng",
          "vendor": "Vates",
          "versions": [
            {
              "status": "affected",
              "version": "all",
              "versionType": "custom"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "finder",
          "value": "Jakob Wolffhechel, Moksha"
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "A vm-admin in XAPI-based hypervisors (XenServer, XCP-ng) can disrupt VM boot by writing an invalid value to VM.HVM_boot_params:firmware or removing the key. XAPI accepts any value at write time but validates at VM start (xapi_xenops.ml:255-268), raising Server_error on invalid values. Firmware key removal causes BIOS fallback, rendering UEFI guests unbootable. The impact is limited because vm-admin already has VM.hard_shutdown capability. The field has zero map_keys_roles entries."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 3.1,
            "baseSeverity": "LOW",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N",
            "version": "3.1"
          },
          "format": "CVSS"
        },
        {
          "cvssV4_0": {
            "baseScore": 5.3,
            "baseSeverity": "MEDIUM",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N",
            "version": "4.0"
          },
          "format": "CVSS"
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-20",
              "description": "Improper Input Validation",
              "lang": "en",
              "type": "CWE"
            }
          ]
        },
        {
          "descriptions": [
            {
              "cweId": "CWE-862",
              "description": "Missing Authorization",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-04-24T06:00:00Z",
        "orgId": "moksha.dk",
        "shortName": "Moksha"
      },
      "references": [
        {
          "url": "https://cna.moksha.dk/MOKSHA-2026-0084"
        }
      ],
      "title": "Firmware Type Denial of Service via VM.HVM_boot_params firmware"
    }
  },
  "cveMetadata": {
    "alternateIds": [
      "GCVE-117-2026-0084"
    ],
    "assignerOrgId": "moksha.dk",
    "cveId": "MOKSHA-2026-0084",
    "datePublished": "2026-04-24T06:00:00Z",
    "state": "PUBLISHED",
    "x_moksha_note": "Self-issued advisory. MOKSHA-2026-NNNN is not a MITRE CVE ID. Schema follows CVE JSON 5.1 for tooling compatibility. alternateIds contains GCVE cross-references (GNA #117) and will also carry MITRE CVE IDs if assigned."
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.1"
}



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