SB2026012780 - Multiple vulnerabilities in Xen

Description

This security bulletin contains information about 3 vulnerabilities.

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

CWE-ID: CWE-264 - Permissions, Privileges, and Access Controls

CVSSv4: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:U/U:Clear

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)

CWE-ID: CWE-367 - Time-of-check Time-of-use (TOCTOU) Race Condition

CVSSv4: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:H/E:U/U:Clear

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)

CWE-ID: CWE-125 - Out-of-bounds read

CVSSv4: CVSS:4.0/AV:L/AC:H/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:U/U:Clear

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