SB2026012780 - Multiple vulnerabilities in Xen

Description

This security bulletin contains information about 3 secuirty vulnerabilities.

1) Permissions, Privileges, and Access Controls (CVE-ID: CVE-2026-23553)

The vulnerability allows a local user to gain access to sensitive information.

The vulnerability exists due to incomplete IBPB for vCPU isolation. A guest processes can leverage information leaks to obtain information intended to be private to other entities in a guest.

2) Time-of-check Time-of-use (TOCTOU) Race Condition (CVE-ID: CVE-2025-58151)

The vulnerability allows a local user to escalate privileges on the system.

The vulnerability exists due to a race condition in varstored. A local user with kernel level access in a VM can escalate privilege via gaining code execution within varstored.

3) Out-of-bounds read (CVE-ID: CVE-2025-58150)

The vulnerability allows a malicious guest to gain access to potentially sensitive information.

The vulnerability exists due to a boundary condition in Xen with shadow paging + tracing on x86 systems. An HVM guests running in shadow paging mode can trigger an out-of-bounds read error and read contents of memory on the system.

Remediation

Install update from vendor's website.

References

• https://xenbits.xen.org/xsa/advisory-479.html
• https://xenbits.xen.org/xsa/advisory-478.html
• https://xenbits.xen.org/xsa/advisory-477.html