Vulnerability-Lookup

CVE-2026-42493 (GCVE-0-2026-42493)

Vulnerability from cvelistv5 – Published: 2026-07-28 12:31 – Updated: 2026-07-28 16:33

Title

x86 shadow paging is deprecated

Summary

Addressing certain issues, in particular related to operations which may take excessively long and therefore would need preemption, has turned out overly costly. Since alternatives (HVM/PVH: HAP, PV: shim) are commonly available, the decision was to deprecate the functionality, while still retaining it for people to use at their own (security) risk. Memory-wise small enough guests may still be okay to run.

Severity

7.5 (High)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

SSVC

Exploitation: none Automatable: yes Technical Impact: partial

CISA Coordinator (v2.0.3)

CWE

CWE-400 - Uncontrolled Resource Consumption

Assigner

XEN

References

3 references

URL	Tags
https://xenbits.xenproject.org/xsa/advisory-495.html
http://xenbits.xen.org/xsa/advisory-495.html
http://www.openwall.com/lists/oss-security/2026/0…

Impacted products

1 product

Vendor	Product	Version
Xen	Xen	Unknown: consult Xen advisory XSA-495

Date Public

2026-07-28 12:00

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "providerMetadata": {
          "dateUpdated": "2026-07-28T16:33:23.792Z",
          "orgId": "af854a3a-2127-422b-91ae-364da2661108",
          "shortName": "CVE"
        },
        "references": [
          {
            "url": "http://xenbits.xen.org/xsa/advisory-495.html"
          },
          {
            "url": "http://www.openwall.com/lists/oss-security/2026/07/28/12"
          }
        ],
        "title": "CVE Program Container"
      },
      {
        "metrics": [
          {
            "cvssV3_1": {
              "attackComplexity": "LOW",
              "attackVector": "NETWORK",
              "availabilityImpact": "HIGH",
              "baseScore": 7.5,
              "baseSeverity": "HIGH",
              "confidentialityImpact": "NONE",
              "integrityImpact": "NONE",
              "privilegesRequired": "NONE",
              "scope": "UNCHANGED",
              "userInteraction": "NONE",
              "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
              "version": "3.1"
            }
          },
          {
            "other": {
              "content": {
                "id": "CVE-2026-42493",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-07-28T15:58:19.075241Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "problemTypes": [
          {
            "descriptions": [
              {
                "cweId": "CWE-400",
                "description": "CWE-400 Uncontrolled Resource Consumption",
                "lang": "en",
                "type": "CWE"
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        "providerMetadata": {
          "dateUpdated": "2026-07-28T15:58:45.484Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "defaultStatus": "unknown",
          "product": "Xen",
          "vendor": "Xen",
          "versions": [
            {
              "status": "unknown",
              "version": "consult Xen advisory XSA-495"
            }
          ]
        }
      ],
      "configurations": [
        {
          "lang": "en",
          "value": "All x86 systems with builds of Xen having SHADOW_PAGING=y are affected.\nNote that prior to Xen 4.7 this control didn\u0027t exist, and all builds of\nXen would be affected.  (Strictly speaking Xen 4.6 had a different, harder\nto use mechanism to disable shadow paging support: One could pass\n\"shadow-paging=n\" on the make command line.)"
        }
      ],
      "datePublic": "2026-07-28T12:00:00.000Z",
      "descriptions": [
        {
          "lang": "en",
          "value": "Addressing certain issues, in particular related to operations which may\ntake excessively long and therefore would need preemption, has turned out\noverly costly.  Since alternatives (HVM/PVH: HAP, PV: shim) are commonly\navailable, the decision was to deprecate the functionality, while still\nretaining it for people to use at their own (security) risk.  Memory-wise\nsmall enough guests may still be okay to run."
        }
      ],
      "impacts": [
        {
          "descriptions": [
            {
              "lang": "en",
              "value": "An unprivileged guest may be able to cause Denial of Service (DoS)\naffecting the entire host."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-07-28T12:31:11.950Z",
        "orgId": "23aa2041-22e1-471f-9209-9b7396fa234f",
        "shortName": "XEN"
      },
      "references": [
        {
          "url": "https://xenbits.xenproject.org/xsa/advisory-495.html"
        }
      ],
      "title": "x86 shadow paging is deprecated",
      "workarounds": [
        {
          "lang": "en",
          "value": "Running HVM and PVH in Hardware Assisted Paging (HAP) mode will avoid this\nvulnerability.\n\nThere\u0027s no mitigation available for PV guests.  This is because shadow\nmode, if support is enabled in the hypervisor, could be engaged at any\ntime.  Note that without shadow mode built into Xen, guests not properly\ndealing with L1TF will simply be crashed instead."
        }
      ]
    }
  },
  "cveMetadata": {
    "assignerOrgId": "23aa2041-22e1-471f-9209-9b7396fa234f",
    "assignerShortName": "XEN",
    "cveId": "CVE-2026-42493",
    "datePublished": "2026-07-28T12:31:11.950Z",
    "dateReserved": "2026-04-27T14:20:24.139Z",
    "dateUpdated": "2026-07-28T16:33:23.792Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-42493\",\"sourceIdentifier\":\"security@xen.org\",\"published\":\"2026-07-28T13:18:32.247\",\"lastModified\":\"2026-07-28T17:16:39.063\",\"vulnStatus\":\"Deferred\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"Addressing certain issues, in particular related to operations which may\\ntake excessively long and therefore would need preemption, has turned out\\noverly costly.  Since alternatives (HVM/PVH: HAP, PV: shim) are commonly\\navailable, the decision was to deprecate the functionality, while still\\nretaining it for people to use at their own (security) risk.  Memory-wise\\nsmall enough guests may still be okay to run.\"}],\"affected\":[{\"source\":\"security@xen.org\",\"affectedData\":[{\"vendor\":\"Xen\",\"product\":\"Xen\",\"defaultStatus\":\"unknown\",\"versions\":[{\"version\":\"consult Xen advisory XSA-495\",\"status\":\"unknown\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H\",\"baseScore\":7.5,\"baseSeverity\":\"HIGH\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"NONE\",\"integrityImpact\":\"NONE\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":3.9,\"impactScore\":3.6}],\"ssvcV203\":[{\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"ssvcData\":{\"timestamp\":\"2026-07-28T15:58:19.075241Z\",\"id\":\"CVE-2026-42493\",\"options\":[{\"exploitation\":\"none\"},{\"automatable\":\"yes\"},{\"technicalImpact\":\"partial\"}],\"role\":\"CISA Coordinator\",\"version\":\"2.0.3\"}}]},\"weaknesses\":[{\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"type\":\"Secondary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-400\"}]}],\"references\":[{\"url\":\"https://xenbits.xenproject.org/xsa/advisory-495.html\",\"source\":\"security@xen.org\"},{\"url\":\"http://www.openwall.com/lists/oss-security/2026/07/28/12\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\"},{\"url\":\"http://xenbits.xen.org/xsa/advisory-495.html\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\"}]}}",
    "vulnrichment": {
      "containers": "{\"adp\": [{\"title\": \"CVE Program Container\", \"references\": [{\"url\": \"http://xenbits.xen.org/xsa/advisory-495.html\"}, {\"url\": \"http://www.openwall.com/lists/oss-security/2026/07/28/12\"}], \"providerMetadata\": {\"orgId\": \"af854a3a-2127-422b-91ae-364da2661108\", \"shortName\": \"CVE\", \"dateUpdated\": \"2026-07-28T16:33:23.792Z\"}}, {\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"cvssV3_1\": {\"scope\": \"UNCHANGED\", \"version\": \"3.1\", \"baseScore\": 7.5, \"attackVector\": \"NETWORK\", \"baseSeverity\": \"HIGH\", \"vectorString\": \"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H\", \"integrityImpact\": \"NONE\", \"userInteraction\": \"NONE\", \"attackComplexity\": \"LOW\", \"availabilityImpact\": \"HIGH\", \"privilegesRequired\": \"NONE\", \"confidentialityImpact\": \"NONE\"}}, {\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-42493\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"yes\"}, {\"Technical Impact\": \"partial\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-07-28T15:58:19.075241Z\"}}}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-400\", \"description\": \"CWE-400 Uncontrolled Resource Consumption\"}]}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-07-28T15:57:59.081Z\"}}], \"cna\": {\"title\": \"x86 shadow paging is deprecated\", \"impacts\": [{\"descriptions\": [{\"lang\": \"en\", \"value\": \"An unprivileged guest may be able to cause Denial of Service (DoS)\\naffecting the entire host.\"}]}], \"affected\": [{\"vendor\": \"Xen\", \"product\": \"Xen\", \"versions\": [{\"status\": \"unknown\", \"version\": \"consult Xen advisory XSA-495\"}], \"defaultStatus\": \"unknown\"}], \"datePublic\": \"2026-07-28T12:00:00.000Z\", \"references\": [{\"url\": \"https://xenbits.xenproject.org/xsa/advisory-495.html\"}], \"workarounds\": [{\"lang\": \"en\", \"value\": \"Running HVM and PVH in Hardware Assisted Paging (HAP) mode will avoid this\\nvulnerability.\\n\\nThere\u0027s no mitigation available for PV guests.  This is because shadow\\nmode, if support is enabled in the hypervisor, could be engaged at any\\ntime.  Note that without shadow mode built into Xen, guests not properly\\ndealing with L1TF will simply be crashed instead.\"}], \"descriptions\": [{\"lang\": \"en\", \"value\": \"Addressing certain issues, in particular related to operations which may\\ntake excessively long and therefore would need preemption, has turned out\\noverly costly.  Since alternatives (HVM/PVH: HAP, PV: shim) are commonly\\navailable, the decision was to deprecate the functionality, while still\\nretaining it for people to use at their own (security) risk.  Memory-wise\\nsmall enough guests may still be okay to run.\"}], \"configurations\": [{\"lang\": \"en\", \"value\": \"All x86 systems with builds of Xen having SHADOW_PAGING=y are affected.\\nNote that prior to Xen 4.7 this control didn\u0027t exist, and all builds of\\nXen would be affected.  (Strictly speaking Xen 4.6 had a different, harder\\nto use mechanism to disable shadow paging support: One could pass\\n\\\"shadow-paging=n\\\" on the make command line.)\"}], \"providerMetadata\": {\"orgId\": \"23aa2041-22e1-471f-9209-9b7396fa234f\", \"shortName\": \"XEN\", \"dateUpdated\": \"2026-07-28T12:31:11.950Z\"}}}",
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}

GHSA-7JXP-562X-944J

Vulnerability from github – Published: 2026-07-28 15:32 – Updated: 2026-07-28 18:33

Details

Severity

7.5 (High)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Show details on source website

JSON

To clipboard

{
  "affected": [],
  "aliases": [
    "CVE-2026-42493"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-400"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-07-28T13:18:32Z",
    "severity": "HIGH"
  },
  "details": "Addressing certain issues, in particular related to operations which may\ntake excessively long and therefore would need preemption, has turned out\noverly costly.  Since alternatives (HVM/PVH: HAP, PV: shim) are commonly\navailable, the decision was to deprecate the functionality, while still\nretaining it for people to use at their own (security) risk.  Memory-wise\nsmall enough guests may still be okay to run.",
  "id": "GHSA-7jxp-562x-944j",
  "modified": "2026-07-28T18:33:02Z",
  "published": "2026-07-28T15:32:17Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-42493"
    },
    {
      "type": "WEB",
      "url": "https://xenbits.xenproject.org/xsa/advisory-495.html"
    },
    {
      "type": "WEB",
      "url": "http://www.openwall.com/lists/oss-security/2026/07/28/12"
    },
    {
      "type": "WEB",
      "url": "http://xenbits.xen.org/xsa/advisory-495.html"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
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.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.

Action not permitted

CVE-2026-42493 (GCVE-0-2026-42493)

GHSA-7JXP-562X-944J

Tags

Sightings

Nomenclature