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ALPINE-CVE-2026-23553

Type: advisorySource: OSV1 source record

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.

Announced Source revision 1
Original source ↗

ALPINE-CVE-2026-23553

Primary source · Revision 1

Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.

Security context

Source reference: osv:ALPINE-CVE-2026-23553

xen

Source reference: /affected/0/package/name

Affected versions
Not stated in this record
Fixed versions
4.18.5-r4

Source reference: /affected/0/ranges

Prerequisites
Not stated in this record

xen

Source reference: /affected/1/package/name

Affected versions
Not stated in this record
Fixed versions
4.19.4-r1

Source reference: /affected/1/ranges

Prerequisites
Not stated in this record

xen

Source reference: /affected/2/package/name

Affected versions
Not stated in this record
Fixed versions
4.20.2-r1

Source reference: /affected/2/ranges

Prerequisites
Not stated in this record

xen

Source reference: /affected/3/package/name

Affected versions
Not stated in this record
Fixed versions
4.20.2-r1

Source reference: /affected/3/ranges

Prerequisites
Not stated in this record

xen

Source reference: /affected/4/package/name

Affected versions
Not stated in this record
Fixed versions
4.21.0-r2

Source reference: /affected/4/ranges

Prerequisites
Not stated in this record

Structured affected-version data

Original package identities and version rules from this source.

[
  {
    "ranges": [
      {
        "type": "ECOSYSTEM",
        "events": [
          {
            "introduced": "4.6.0"
          },
          {
            "fixed": "4.18.5-r4"
          }
        ]
      }
    ],
    "package": {
      "name": "xen",
      "purl": "pkg:apk/alpine/xen?arch=source",
      "ecosystem": "Alpine:v3.20"
    },
    "database_specific": {
      "source": "https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2026-23553.json"
    },
    "ecosystem_specific": {}
  },
  {
    "ranges": [
      {
        "type": "ECOSYSTEM",
        "events": [
          {
            "introduced": "4.6.0"
          },
          {
            "fixed": "4.19.4-r1"
          }
        ]
      }
    ],
    "package": {
      "name": "xen",
      "purl": "pkg:apk/alpine/xen?arch=source",
      "ecosystem": "Alpine:v3.21"
    },
    "database_specific": {
      "source": "https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2026-23553.json"
    },
    "ecosystem_specific": {}
  },
  {
    "ranges": [
      {
        "type": "ECOSYSTEM",
        "events": [
          {
            "introduced": "4.6.0"
          },
          {
            "fixed": "4.20.2-r1"
          }
        ]
      }
    ],
    "package": {
      "name": "xen",
      "purl": "pkg:apk/alpine/xen?arch=source",
      "ecosystem": "Alpine:v3.22"
    },
    "database_specific": {
      "source": "https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2026-23553.json"
    },
    "ecosystem_specific": {}
  },
  {
    "ranges": [
      {
        "type": "ECOSYSTEM",
        "events": [
          {
            "introduced": "4.6.0"
          },
          {
            "fixed": "4.20.2-r1"
          }
        ]
      }
    ],
    "package": {
      "name": "xen",
      "purl": "pkg:apk/alpine/xen?arch=source",
      "ecosystem": "Alpine:v3.23"
    },
    "database_specific": {
      "source": "https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2026-23553.json"
    },
    "ecosystem_specific": {}
  },
  {
    "ranges": [
      {
        "type": "ECOSYSTEM",
        "events": [
          {
            "introduced": "4.6.0"
          },
          {
            "fixed": "4.21.0-r2"
          }
        ]
      }
    ],
    "package": {
      "name": "xen",
      "purl": "pkg:apk/alpine/xen?arch=source",
      "ecosystem": "Alpine:v3.24"
    },
    "database_specific": {
      "source": "https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2026-23553.json"
    },
    "ecosystem_specific": {}
  }
]

Publisher severity

No explicit severity was provided.

Event
#54177 · Revision 1
Added to Heist Feed
Publisher date
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