Integer underflow in Xen - CVE-2026-42495
Published: July 29, 2026
Vulnerability identifier: #VU140028
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2026-42495
CWE-ID: CWE-191
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Affected software:
Xen
Xen
Detailed vulnerability description
The vulnerability allows a remote user to escalate privileges.
The vulnerability exists due to an integer underflow in libfsimage's iso9660 System Use area calculation when parsing a crafted iso9660 filesystem image. A remote user can provide a crafted disk image to pygrub to escalate privileges.
Exploitation requires a guest to use the pygrub bootloader.
How to mitigate CVE-2026-42495
Install security update from vendor's website.