Vulnerability-Lookup

CVE-2026-23553 (GCVE-0-2026-23553)

Vulnerability from cvelistv5 – Published: 2026-01-28 15:33 – Updated: 2026-01-28 16:41

Title

x86: incomplete IBPB for vCPU isolation

Summary

In the context switch logic Xen attempts to skip an IBPB in the case of a vCPU returning to a CPU on which it was the previous vCPU to run. While safe for Xen's isolation between vCPUs, this prevents the guest kernel correctly isolating between tasks. Consider: 1) vCPU runs on CPU A, running task 1. 2) vCPU moves to CPU B, idle gets scheduled on A. Xen skips IBPB. 3) On CPU B, guest kernel switches from task 1 to 2, issuing IBPB. 4) vCPU moves back to CPU A. Xen skips IBPB again. Now, task 2 is running on CPU A with task 1's training still in the BTB.

Severity ?

2.9 (Low)


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

CWE

CWE-665 - Improper Initialization
CWE-693 - Protection Mechanism Failure

Assigner

XEN

References

URL

Tags

https://xenbits.xenproject.org/xsa/advisory-479.html

Impacted products

	Vendor	Product	Version
	Xen	Xen	Unknown: consult Xen advisory XSA-479

Credits

This issue was discovered by David Kaplan of AMD.

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
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        "providerMetadata": {
          "dateUpdated": "2026-01-28T16:12:31.841Z",
          "orgId": "af854a3a-2127-422b-91ae-364da2661108",
          "shortName": "CVE"
        },
        "references": [
          {
            "url": "http://www.openwall.com/lists/oss-security/2026/01/27/3"
          },
          {
            "url": "http://xenbits.xen.org/xsa/advisory-479.html"
          }
        ],
        "title": "CVE Program Container"
      },
      {
        "metrics": [
          {
            "cvssV3_1": {
              "attackComplexity": "HIGH",
              "attackVector": "LOCAL",
              "availabilityImpact": "NONE",
              "baseScore": 2.9,
              "baseSeverity": "LOW",
              "confidentialityImpact": "LOW",
              "integrityImpact": "NONE",
              "privilegesRequired": "NONE",
              "scope": "UNCHANGED",
              "userInteraction": "NONE",
              "vectorString": "CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N",
              "version": "3.1"
            }
          },
          {
            "other": {
              "content": {
                "id": "CVE-2026-23553",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-01-28T16:40:38.385640Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "problemTypes": [
          {
            "descriptions": [
              {
                "cweId": "CWE-665",
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                "lang": "en",
                "type": "CWE"
              }
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          },
          {
            "descriptions": [
              {
                "cweId": "CWE-693",
                "description": "CWE-693 Protection Mechanism Failure",
                "lang": "en",
                "type": "CWE"
              }
            ]
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-01-28T16:41:14.803Z",
          "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-479"
            }
          ]
        }
      ],
      "configurations": [
        {
          "lang": "en",
          "value": "Xen versions which had the XSA-254 fixes backported are vulnerable.\nUpstream, that is 4.6 and newer.\n\nOnly x86 systems are vulnerable.  Arm systems are not vulerable.\n\nSystems vulnerable to SRSO (see XSA-434) with default settings use\nIBPB-on-entry to protect against SRSO.  This is a rather more aggressive\nform of flushing than only on context switch, and is believed to be\nsufficient to avoid the vulnerability."
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "finder",
          "value": "This issue was discovered by David Kaplan of AMD."
        }
      ],
      "datePublic": "2026-01-27T12:00:00.000Z",
      "descriptions": [
        {
          "lang": "en",
          "value": "In the context switch logic Xen attempts to skip an IBPB in the case of\na vCPU returning to a CPU on which it was the previous vCPU to run.\nWhile safe for Xen\u0027s isolation between vCPUs, this prevents the guest\nkernel correctly isolating between tasks.  Consider:\n\n 1) vCPU runs on CPU A, running task 1.\n 2) vCPU moves to CPU B, idle gets scheduled on A.  Xen skips IBPB.\n 3) On CPU B, guest kernel switches from task 1 to 2, issuing IBPB.\n 4) vCPU moves back to CPU A.  Xen skips IBPB again.\n\nNow, task 2 is running on CPU A with task 1\u0027s training still in the BTB."
        }
      ],
      "impacts": [
        {
          "descriptions": [
            {
              "lang": "en",
              "value": "Guest processes may leverage information leaks to obtain information\nintended to be private to other entities in a guest."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-01-28T15:33:44.782Z",
        "orgId": "23aa2041-22e1-471f-9209-9b7396fa234f",
        "shortName": "XEN"
      },
      "references": [
        {
          "url": "https://xenbits.xenproject.org/xsa/advisory-479.html"
        }
      ],
      "title": "x86: incomplete IBPB for vCPU isolation",
      "workarounds": [
        {
          "lang": "en",
          "value": "Using \"spec-ctrl=ibpb-entry=hvm,ibpb-entry=pv\" on the Xen command line\nwill activate the SRSO mitigation on non-SRSO-vulnerable hardware, but\nit is a large overhead."
        }
      ]
    }
  },
  "cveMetadata": {
    "assignerOrgId": "23aa2041-22e1-471f-9209-9b7396fa234f",
    "assignerShortName": "XEN",
    "cveId": "CVE-2026-23553",
    "datePublished": "2026-01-28T15:33:44.782Z",
    "dateReserved": "2026-01-14T13:07:36.961Z",
    "dateUpdated": "2026-01-28T16:41:14.803Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-23553\",\"sourceIdentifier\":\"security@xen.org\",\"published\":\"2026-01-28T16:16:16.853\",\"lastModified\":\"2026-01-28T17:16:15.990\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the context switch logic Xen attempts to skip an IBPB in the case of\\na vCPU returning to a CPU on which it was the previous vCPU to run.\\nWhile safe for Xen\u0027s isolation between vCPUs, this prevents the guest\\nkernel correctly isolating between tasks.  Consider:\\n\\n 1) vCPU runs on CPU A, running task 1.\\n 2) vCPU moves to CPU B, idle gets scheduled on A.  Xen skips IBPB.\\n 3) On CPU B, guest kernel switches from task 1 to 2, issuing IBPB.\\n 4) vCPU moves back to CPU A.  Xen skips IBPB again.\\n\\nNow, task 2 is running on CPU A with task 1\u0027s training still in the BTB.\"}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N\",\"baseScore\":2.9,\"baseSeverity\":\"LOW\",\"attackVector\":\"LOCAL\",\"attackComplexity\":\"HIGH\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"LOW\",\"integrityImpact\":\"NONE\",\"availabilityImpact\":\"NONE\"},\"exploitabilityScore\":1.4,\"impactScore\":1.4}]},\"weaknesses\":[{\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"type\":\"Secondary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-665\"},{\"lang\":\"en\",\"value\":\"CWE-693\"}]}],\"references\":[{\"url\":\"https://xenbits.xenproject.org/xsa/advisory-479.html\",\"source\":\"security@xen.org\"},{\"url\":\"http://www.openwall.com/lists/oss-security/2026/01/27/3\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\"},{\"url\":\"http://xenbits.xen.org/xsa/advisory-479.html\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\"}]}}",
    "vulnrichment": {
      "containers": "{\"adp\": [{\"title\": \"CVE Program Container\", \"references\": [{\"url\": \"http://www.openwall.com/lists/oss-security/2026/01/27/3\"}, {\"url\": \"http://xenbits.xen.org/xsa/advisory-479.html\"}], \"providerMetadata\": {\"orgId\": \"af854a3a-2127-422b-91ae-364da2661108\", \"shortName\": \"CVE\", \"dateUpdated\": \"2026-01-28T16:12:31.841Z\"}}, {\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"cvssV3_1\": {\"scope\": \"UNCHANGED\", \"version\": \"3.1\", \"baseScore\": 2.9, \"attackVector\": \"LOCAL\", \"baseSeverity\": \"LOW\", \"vectorString\": \"CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N\", \"integrityImpact\": \"NONE\", \"userInteraction\": \"NONE\", \"attackComplexity\": \"HIGH\", \"availabilityImpact\": \"NONE\", \"privilegesRequired\": \"NONE\", \"confidentialityImpact\": \"LOW\"}}, {\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-23553\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"no\"}, {\"Technical Impact\": \"partial\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-01-28T16:40:38.385640Z\"}}}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-665\", \"description\": \"CWE-665 Improper Initialization\"}]}, {\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-693\", \"description\": \"CWE-693 Protection Mechanism Failure\"}]}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-01-28T16:39:51.548Z\"}}], \"cna\": {\"title\": \"x86: incomplete IBPB for vCPU isolation\", \"credits\": [{\"lang\": \"en\", \"type\": \"finder\", \"value\": \"This issue was discovered by David Kaplan of AMD.\"}], \"impacts\": [{\"descriptions\": [{\"lang\": \"en\", \"value\": \"Guest processes may leverage information leaks to obtain information\\nintended to be private to other entities in a guest.\"}]}], \"affected\": [{\"vendor\": \"Xen\", \"product\": \"Xen\", \"versions\": [{\"status\": \"unknown\", \"version\": \"consult Xen advisory XSA-479\"}], \"defaultStatus\": \"unknown\"}], \"datePublic\": \"2026-01-27T12:00:00.000Z\", \"references\": [{\"url\": \"https://xenbits.xenproject.org/xsa/advisory-479.html\"}], \"workarounds\": [{\"lang\": \"en\", \"value\": \"Using \\\"spec-ctrl=ibpb-entry=hvm,ibpb-entry=pv\\\" on the Xen command line\\nwill activate the SRSO mitigation on non-SRSO-vulnerable hardware, but\\nit is a large overhead.\"}], \"descriptions\": [{\"lang\": \"en\", \"value\": \"In the context switch logic Xen attempts to skip an IBPB in the case of\\na vCPU returning to a CPU on which it was the previous vCPU to run.\\nWhile safe for Xen\u0027s isolation between vCPUs, this prevents the guest\\nkernel correctly isolating between tasks.  Consider:\\n\\n 1) vCPU runs on CPU A, running task 1.\\n 2) vCPU moves to CPU B, idle gets scheduled on A.  Xen skips IBPB.\\n 3) On CPU B, guest kernel switches from task 1 to 2, issuing IBPB.\\n 4) vCPU moves back to CPU A.  Xen skips IBPB again.\\n\\nNow, task 2 is running on CPU A with task 1\u0027s training still in the BTB.\"}], \"configurations\": [{\"lang\": \"en\", \"value\": \"Xen versions which had the XSA-254 fixes backported are vulnerable.\\nUpstream, that is 4.6 and newer.\\n\\nOnly x86 systems are vulnerable.  Arm systems are not vulerable.\\n\\nSystems vulnerable to SRSO (see XSA-434) with default settings use\\nIBPB-on-entry to protect against SRSO.  This is a rather more aggressive\\nform of flushing than only on context switch, and is believed to be\\nsufficient to avoid the vulnerability.\"}], \"providerMetadata\": {\"orgId\": \"23aa2041-22e1-471f-9209-9b7396fa234f\", \"shortName\": \"XEN\", \"dateUpdated\": \"2026-01-28T15:33:44.782Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-23553\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-01-28T16:41:14.803Z\", \"dateReserved\": \"2026-01-14T13:07:36.961Z\", \"assignerOrgId\": \"23aa2041-22e1-471f-9209-9b7396fa234f\", \"datePublished\": \"2026-01-28T15:33:44.782Z\", \"assignerShortName\": \"XEN\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
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}

CERTFR-2026-AVI-0091

Vulnerability from certfr_avis - Published: 2026-01-27 - Updated: 2026-01-27

De multiples vulnérabilités ont été découvertes dans Xen. Certaines d'entre elles permettent à un attaquant de provoquer une élévation de privilèges, un déni de service à distance et une atteinte à la confidentialité des données.

Solutions

Se référer au bulletin de sécurité de l'éditeur pour l'obtention des correctifs (cf. section Documentation).

Impacted products

Vendor	Product	Description
XEN	Xen	Xen versions xen-unstable sans les correctifs de sécurité xsa477.patch et xsa479.patch
XEN	Xen	Xen versions 4.18.x sans les correctifs de sécurité xsa477-4.18.patch et xsa479.patch
XEN	Xen	Xen versions 4.19.x sans le correctif de securité xsa477.patch
XEN	Xen	Xen version varstored master sans le correctif de sécurité xsa478.patch

References

Title

Publication Time

Tags

Bulletin de sécurité Xen xsa/advisory-477	2026-01-27	vendor-advisory
Bulletin de sécurité Xen xsa/advisory-478	2026-01-27	vendor-advisory
Bulletin de sécurité Xen xsa/advisory-479	2026-01-27	vendor-advisory

Show details on source website

JSON

To clipboard

{
  "$ref": "https://www.cert.ssi.gouv.fr/openapi.json",
  "affected_systems": [
    {
      "description": "Xen versions xen-unstable sans les correctifs de s\u00e9curit\u00e9 xsa477.patch et xsa479.patch",
      "product": {
        "name": "Xen",
        "vendor": {
          "name": "XEN",
          "scada": false
        }
      }
    },
    {
      "description": "Xen versions 4.18.x sans les correctifs de s\u00e9curit\u00e9 xsa477-4.18.patch et xsa479.patch",
      "product": {
        "name": "Xen",
        "vendor": {
          "name": "XEN",
          "scada": false
        }
      }
    },
    {
      "description": "Xen versions 4.19.x sans le correctif de securit\u00e9 xsa477.patch",
      "product": {
        "name": "Xen",
        "vendor": {
          "name": "XEN",
          "scada": false
        }
      }
    },
    {
      "description": "Xen version varstored master sans le correctif de s\u00e9curit\u00e9 xsa478.patch",
      "product": {
        "name": "Xen",
        "vendor": {
          "name": "XEN",
          "scada": false
        }
      }
    }
  ],
  "affected_systems_content": "",
  "content": "## Solutions\n\nSe r\u00e9f\u00e9rer au bulletin de s\u00e9curit\u00e9 de l\u0027\u00e9diteur pour l\u0027obtention des correctifs (cf. section Documentation).",
  "cves": [
    {
      "name": "CVE-2026-23553",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-23553"
    },
    {
      "name": "CVE-2025-58151",
      "url": "https://www.cve.org/CVERecord?id=CVE-2025-58151"
    },
    {
      "name": "CVE-2025-58150",
      "url": "https://www.cve.org/CVERecord?id=CVE-2025-58150"
    }
  ],
  "initial_release_date": "2026-01-27T00:00:00",
  "last_revision_date": "2026-01-27T00:00:00",
  "links": [],
  "reference": "CERTFR-2026-AVI-0091",
  "revisions": [
    {
      "description": "Version initiale",
      "revision_date": "2026-01-27T00:00:00.000000"
    }
  ],
  "risks": [
    {
      "description": "D\u00e9ni de service \u00e0 distance"
    },
    {
      "description": "Atteinte \u00e0 la confidentialit\u00e9 des donn\u00e9es"
    },
    {
      "description": "\u00c9l\u00e9vation de privil\u00e8ges"
    }
  ],
  "summary": "De multiples vuln\u00e9rabilit\u00e9s ont \u00e9t\u00e9 d\u00e9couvertes dans Xen. Certaines d\u0027entre elles permettent \u00e0 un attaquant de provoquer une \u00e9l\u00e9vation de privil\u00e8ges, un d\u00e9ni de service \u00e0 distance et une atteinte \u00e0 la confidentialit\u00e9 des donn\u00e9es.",
  "title": "Multiples vuln\u00e9rabilit\u00e9s dans Xen",
  "vendor_advisories": [
    {
      "published_at": "2026-01-27",
      "title": "Bulletin de s\u00e9curit\u00e9 Xen xsa/advisory-477",
      "url": "https://xenbits.xen.org/xsa/advisory-477.html"
    },
    {
      "published_at": "2026-01-27",
      "title": "Bulletin de s\u00e9curit\u00e9 Xen xsa/advisory-478",
      "url": "https://xenbits.xen.org/xsa/advisory-478.html"
    },
    {
      "published_at": "2026-01-27",
      "title": "Bulletin de s\u00e9curit\u00e9 Xen xsa/advisory-479",
      "url": "https://xenbits.xen.org/xsa/advisory-479.html"
    }
  ]
}

CERTFR-2026-AVI-0090

Vulnerability from certfr_avis - Published: 2026-01-27 - Updated: 2026-01-27

De multiples vulnérabilités ont été découvertes dans Citrix XenServer. Elles permettent à un attaquant de provoquer un déni de service à distance et une atteinte à la confidentialité des données.

Solutions

Se référer au bulletin de sécurité de l'éditeur pour l'obtention des correctifs (cf. section Documentation).

Impacted products

	Vendor	Product	Description
	Citrix	XenServer	XenServer version 8.4 sans le dernier correctif de sécurité

References

Title

Publication Time

Tags

Bulletin de sécurité Citrix CTX695997

2026-01-27

vendor-advisory

Show details on source website

JSON

To clipboard

{
  "$ref": "https://www.cert.ssi.gouv.fr/openapi.json",
  "affected_systems": [
    {
      "description": "XenServer version 8.4 sans le dernier correctif de s\u00e9curit\u00e9",
      "product": {
        "name": "XenServer",
        "vendor": {
          "name": "Citrix",
          "scada": false
        }
      }
    }
  ],
  "affected_systems_content": "",
  "content": "## Solutions\n\nSe r\u00e9f\u00e9rer au bulletin de s\u00e9curit\u00e9 de l\u0027\u00e9diteur pour l\u0027obtention des correctifs (cf. section Documentation).",
  "cves": [
    {
      "name": "CVE-2026-23553",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-23553"
    },
    {
      "name": "CVE-2025-58151",
      "url": "https://www.cve.org/CVERecord?id=CVE-2025-58151"
    }
  ],
  "initial_release_date": "2026-01-27T00:00:00",
  "last_revision_date": "2026-01-27T00:00:00",
  "links": [],
  "reference": "CERTFR-2026-AVI-0090",
  "revisions": [
    {
      "description": "Version initiale",
      "revision_date": "2026-01-27T00:00:00.000000"
    }
  ],
  "risks": [
    {
      "description": "D\u00e9ni de service \u00e0 distance"
    },
    {
      "description": "Atteinte \u00e0 la confidentialit\u00e9 des donn\u00e9es"
    }
  ],
  "summary": "De multiples vuln\u00e9rabilit\u00e9s ont \u00e9t\u00e9 d\u00e9couvertes dans Citrix XenServer. Elles permettent \u00e0 un attaquant de provoquer un d\u00e9ni de service \u00e0 distance et une atteinte \u00e0 la confidentialit\u00e9 des donn\u00e9es.",
  "title": "Multiples vuln\u00e9rabilit\u00e9s dans Citrix XenServer",
  "vendor_advisories": [
    {
      "published_at": "2026-01-27",
      "title": "Bulletin de s\u00e9curit\u00e9 Citrix CTX695997",
      "url": "https://support.citrix.com/support-home/kbsearch/article?articleNumber=CTX695997\u0026articleURL=XenServer_Security_Update_for_CVE_2025_58151_and_CVE_2026_23553"
    }
  ]
}

GHSA-PXQC-5JG3-XFQM

Vulnerability from github – Published: 2026-01-28 18:30 – Updated: 2026-01-28 18:30

Details

1) vCPU runs on CPU A, running task 1. 2) vCPU moves to CPU B, idle gets scheduled on A. Xen skips IBPB. 3) On CPU B, guest kernel switches from task 1 to 2, issuing IBPB. 4) vCPU moves back to CPU A. Xen skips IBPB again.

Now, task 2 is running on CPU A with task 1's training still in the BTB.

Severity ?

2.9 (Low)


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

Show details on source website

JSON

To clipboard

{
  "affected": [],
  "aliases": [
    "CVE-2026-23553"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-665"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-01-28T16:16:16Z",
    "severity": "LOW"
  },
  "details": "In the context switch logic Xen attempts to skip an IBPB in the case of\na vCPU returning to a CPU on which it was the previous vCPU to run.\nWhile safe for Xen\u0027s isolation between vCPUs, this prevents the guest\nkernel correctly isolating between tasks.  Consider:\n\n 1) vCPU runs on CPU A, running task 1.\n 2) vCPU moves to CPU B, idle gets scheduled on A.  Xen skips IBPB.\n 3) On CPU B, guest kernel switches from task 1 to 2, issuing IBPB.\n 4) vCPU moves back to CPU A.  Xen skips IBPB again.\n\nNow, task 2 is running on CPU A with task 1\u0027s training still in the BTB.",
  "id": "GHSA-pxqc-5jg3-xfqm",
  "modified": "2026-01-28T18:30:47Z",
  "published": "2026-01-28T18:30:47Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-23553"
    },
    {
      "type": "WEB",
      "url": "https://xenbits.xenproject.org/xsa/advisory-479.html"
    },
    {
      "type": "WEB",
      "url": "http://www.openwall.com/lists/oss-security/2026/01/27/3"
    },
    {
      "type": "WEB",
      "url": "http://xenbits.xen.org/xsa/advisory-479.html"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N",
      "type": "CVSS_V3"
    }
  ]
}

FKIE_CVE-2026-23553

Vulnerability from fkie_nvd - Published: 2026-01-28 16:16 - Updated: 2026-01-28 17:16

Severity ?

2.9 (Low) - CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N

Summary

References

	URL	Tags
	security@xen.org	https://xenbits.xenproject.org/xsa/advisory-479.html
	af854a3a-2127-422b-91ae-364da2661108	http://www.openwall.com/lists/oss-security/2026/01/27/3
	af854a3a-2127-422b-91ae-364da2661108	http://xenbits.xen.org/xsa/advisory-479.html

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the context switch logic Xen attempts to skip an IBPB in the case of\na vCPU returning to a CPU on which it was the previous vCPU to run.\nWhile safe for Xen\u0027s isolation between vCPUs, this prevents the guest\nkernel correctly isolating between tasks.  Consider:\n\n 1) vCPU runs on CPU A, running task 1.\n 2) vCPU moves to CPU B, idle gets scheduled on A.  Xen skips IBPB.\n 3) On CPU B, guest kernel switches from task 1 to 2, issuing IBPB.\n 4) vCPU moves back to CPU A.  Xen skips IBPB again.\n\nNow, task 2 is running on CPU A with task 1\u0027s training still in the BTB."
    }
  ],
  "id": "CVE-2026-23553",
  "lastModified": "2026-01-28T17:16:15.990",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "HIGH",
          "attackVector": "LOCAL",
          "availabilityImpact": "NONE",
          "baseScore": 2.9,
          "baseSeverity": "LOW",
          "confidentialityImpact": "LOW",
          "integrityImpact": "NONE",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 1.4,
        "impactScore": 1.4,
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-01-28T16:16:16.853",
  "references": [
    {
      "source": "security@xen.org",
      "url": "https://xenbits.xenproject.org/xsa/advisory-479.html"
    },
    {
      "source": "af854a3a-2127-422b-91ae-364da2661108",
      "url": "http://www.openwall.com/lists/oss-security/2026/01/27/3"
    },
    {
      "source": "af854a3a-2127-422b-91ae-364da2661108",
      "url": "http://xenbits.xen.org/xsa/advisory-479.html"
    }
  ],
  "sourceIdentifier": "security@xen.org",
  "vulnStatus": "Received",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-665"
        },
        {
          "lang": "en",
          "value": "CWE-693"
        }
      ],
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "type": "Secondary"
    }
  ]
}

Tags

Taxonomy of the tags.

All sightings related to this event Export sightings related to this event

Sightings

Author	Source	Type	Date

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.

Action not permitted

CVE-2026-23553 (GCVE-0-2026-23553)

CERTFR-2026-AVI-0091

Solutions

CERTFR-2026-AVI-0090

Solutions

GHSA-PXQC-5JG3-XFQM

FKIE_CVE-2026-23553

Tags

Sightings

Nomenclature