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.

The remote SUSE Linux SLED15 / SLED_SAP15 / SLES15 / SLES_SAP15 host has packages installed that are affected by multiple vulnerabilities as referenced in the SUSE-SU-2026:0589-1 advisory.

    - CVE-2025-58150: buffer overrun with shadow paging + tracing (XSA-477) (bsc#1256745).
    - CVE-2026-23553: incomplete IBPB for vCPU isolation (XSA-479) (bsc#1256747).

Tenable has extracted the preceding description block directly from the SUSE security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote Fedora 42 host has a package installed that is affected by multiple vulnerabilities as referenced in the FEDORA-2026-e39149a8a0 advisory.

    x86: buffer overrun with shadow paging + tracing [XSA-477, CVE-2025-58150]     x86: incomplete IBPB for vCPU isolation [XSA-479, CVE-2026-23553]

Tenable has extracted the preceding description block directly from the Fedora security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote Fedora 43 host has a package installed that is affected by multiple vulnerabilities as referenced in the FEDORA-2026-844012d662 advisory.

    x86: buffer overrun with shadow paging + tracing [XSA-477, CVE-2025-58150]     x86: incomplete IBPB for vCPU isolation [XSA-479, CVE-2026-23553]

Tenable has extracted the preceding description block directly from the Fedora security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote SUSE Linux SLES12 host has packages installed that are affected by multiple vulnerabilities as referenced in the SUSE-SU-2026:0328-1 advisory.

    Security fixes:

    - CVE-2025-58150: Fixed buffer overrun with shadow paging and       tracing (XSA-477) (bsc#1256745)
    - CVE-2026-23553: Fixed incomplete IBPB for vCPU isolation       (XSA-479) (bsc#1256747)
    - CVE-2025-58149: Fixed incorrect removal od permissions on PCI       device unplug allow PV guests to access memory of devices no       longer assigned to it (XSA-476) (bsc#1252692)

Tenable has extracted the preceding description block directly from the SUSE security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote SUSE Linux SLED15 / SLED_SAP15 / SLES15 / SLES_SAP15 host has packages installed that are affected by multiple vulnerabilities as referenced in the SUSE-SU-2026:0329-1 advisory.

    - CVE-2025-58150: Fixed buffer overrun with shadow paging and       tracing (XSA-477) (bsc#1256745)
    - CVE-2026-23553: Fixed incomplete IBPB for vCPU isolation       (XSA-479) (bsc#1256747)

Tenable has extracted the preceding description block directly from the SUSE security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote openSUSE 15 host has packages installed that are affected by multiple vulnerabilities as referenced in the SUSE-SU-2026:0306-1 advisory.

    - CVE-2025-58150: Fixed buffer overrun with shadow paging and       tracing (XSA-477) (bsc#1256745)
    - CVE-2026-23553: Fixed incomplete IBPB for vCPU isolation       (XSA-479) (bsc#1256747)

Tenable has extracted the preceding description block directly from the SUSE security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

There are packages installed that are affected by multiple vulnerabilities referenced in the following CVEs:

  - Shadow mode tracing code uses a set of per-CPU variables to avoid cumbersome parameter passing. Some of
    these variables are written to with guest controlled data, of guest controllable size. That size can be
    larger than the variable, and bounding of the writes was missing. (CVE-2025-58150)

  - 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. (CVE-2026-23553)

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - 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. (CVE-2026-23553)

Note that Nessus relies on the presence of the package as reported by the vendor.

ID	Name	Product	Family	Severity
299716	SUSE SLED15 / SLES15 Security Update : xen (SUSE-SU-2026:0589-1)	Nessus	SuSE Local Security Checks	high
299134	Fedora 42 : xen (2026-e39149a8a0)	Nessus	Fedora Local Security Checks	high
297756	Fedora 43 : xen (2026-844012d662)	Nessus	Fedora Local Security Checks	high
297200	SUSE SLES12: xen / xen-devel / xen-doc-html / xen-libs / xen-libs-32bit / etc (SUSE-SU-2026:0328-1)	Nessus	SuSE Local Security Checks	high
297193	SUSE SLED15: xen / xen-devel / xen-libs / xen-tools / xen-tools-domU / etc (SUSE-SU-2026:0329-1)	Nessus	SuSE Local Security Checks	high
297088	openSUSE 15: xen / xen-devel / xen-doc-html / xen-libs / xen-libs-32bit / etc (SUSE-SU-2026:0306-1)	Nessus	SuSE Local Security Checks	high
437350	Alpine: multiple xen packages: security update to 4.20.2-r1	Tenable Cloud Security	Alpine Linux Local Security Checks	high
437350	Alpine: multiple xen packages: security update to 4.20.2-r1	Tenable Self-Hosted Container Security	Alpine Linux Local Security Checks	high
437349	Alpine: multiple xen packages: security update to 4.18.5-r4	Tenable Cloud Security	Alpine Linux Local Security Checks	high
437349	Alpine: multiple xen packages: security update to 4.18.5-r4	Tenable Self-Hosted Container Security	Alpine Linux Local Security Checks	high
437348	Alpine: multiple xen packages: security update to 4.19.4-r1	Tenable Cloud Security	Alpine Linux Local Security Checks	high
437348	Alpine: multiple xen packages: security update to 4.19.4-r1	Tenable Self-Hosted Container Security	Alpine Linux Local Security Checks	high
296898	Linux Distros Unpatched Vulnerability : CVE-2026-23553	Nessus	Misc.	low

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