Out-of-bounds read in Xen - CVE-2026-31786

Vulnerability identifier: #VU128377

CSH Severity: Low

CVSS v4: 8.5 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-31786

CWE-ID: CWE-125

Exploitation vector: Local access

Exploit availability: No public exploit available

The vulnerability allows a local user to disclose sensitive information, cause a denial of service, or escalate privileges.

The vulnerability exists due to an out-of-bounds read in the Xen-related sysfs buildid handler when reading the /sys/hypervisor/properties/buildid sysfs file. A local user can read the crafted sysfs output to disclose sensitive information, cause a denial of service, or escalate privileges.

In rare cases, the issue may also result in writing past the 4 kB sysfs buffer if no zero byte is found in adjacent data.

Xen
Debian Linux
Anolis OS
Red Hat CodeReady Linux Builder for ARM 64
Red Hat CodeReady Linux Builder for Power, little endian
Red Hat CodeReady Linux Builder for x86_64
Red Hat Enterprise Linux for ARM 64
Red Hat Enterprise Linux for Power, little endian
Red Hat Enterprise Linux for IBM z Systems
Red Hat Enterprise Linux for x86_64
Red Hat Enterprise Linux for Real Time for NFV
Red Hat Enterprise Linux for Real Time
openEuler
kernel (Red Hat package)
kernel-rt (Red Hat package)
kernel-headers
kernel-core
kernel-cross-headers
kernel-debug
kernel-debug-core
kernel-debug-devel
kernel-debug-modules
kernel-debug-modules-extra
kernel-devel
bpftool
kernel-modules
kernel-modules-extra
kernel-tools
kernel-tools-libs
kernel-tools-libs-devel
perf
python3-perf
kernel-abi-stablelists
kernel-doc
kernel
bpftool-debuginfo
kernel-debuginfo
kernel-debugsource
kernel-source
kernel-tools-debuginfo
kernel-tools-devel
perf-debuginfo
python3-perf-debuginfo
linux (Debian package)

Install security update from vendor's website.

kernel (Red Hat package) - addressed in versions 4.18.0-553.134.1.el8_10, 6.12.0-211.26.1.el10_2
kernel-rt (Red Hat package) - update to 4.18.0-553.134.1.rt7.475.el8_10
kernel-headers - update to 4.18.0-553.137.1.0.1
kernel-core - update to 4.18.0-553.137.1.0.1
kernel-cross-headers - update to 4.18.0-553.137.1.0.1
kernel-debug - update to 4.18.0-553.137.1.0.1
kernel-debug-core - update to 4.18.0-553.137.1.0.1
kernel-debug-devel - update to 4.18.0-553.137.1.0.1
kernel-debug-modules - update to 4.18.0-553.137.1.0.1
kernel-debug-modules-extra - update to 4.18.0-553.137.1.0.1
kernel-devel - update to 4.18.0-553.137.1.0.1
bpftool - update to 4.18.0-553.137.1.0.1
kernel-modules - update to 4.18.0-553.137.1.0.1
kernel-modules-extra - update to 4.18.0-553.137.1.0.1
kernel-tools - update to 4.18.0-553.137.1.0.1
kernel-tools-libs - update to 4.18.0-553.137.1.0.1
kernel-tools-libs-devel - update to 4.18.0-553.137.1.0.1
perf - update to 4.18.0-553.137.1.0.1
python3-perf - update to 4.18.0-553.137.1.0.1
kernel-abi-stablelists - update to 4.18.0-553.137.1.0.1
kernel-doc - update to 4.18.0-553.137.1.0.1
kernel - update to 4.18.0-553.137.1.0.1
bpftool - update to 5.10.0-318.0.0.221
bpftool-debuginfo - update to 5.10.0-318.0.0.221
kernel-debuginfo - update to 5.10.0-318.0.0.221
kernel-debugsource - update to 5.10.0-318.0.0.221
kernel-devel - update to 5.10.0-318.0.0.221
kernel-headers - update to 5.10.0-318.0.0.221
kernel-source - update to 5.10.0-318.0.0.221
kernel-tools - update to 5.10.0-318.0.0.221
kernel-tools-debuginfo - update to 5.10.0-318.0.0.221
kernel-tools-devel - update to 5.10.0-318.0.0.221
perf - update to 5.10.0-318.0.0.221
perf-debuginfo - update to 5.10.0-318.0.0.221
python3-perf - update to 5.10.0-318.0.0.221
python3-perf-debuginfo - update to 5.10.0-318.0.0.221
kernel - update to 5.10.0-318.0.0.221
linux (Debian package) - addressed in versions 6.1.170-1, 6.12.85-1

• https://xenbits.xen.org/xsa/advisory-485.html

• Multiple vulnerabilities in Xen
• Debian update for linux
• Debian update for linux
• openEuler 22.03 LTS SP4 update for kernel
• Red Hat Enterprise Linux 8 update for kernel-rt
• Red Hat Enterprise Linux 10 update for kernel
• Red Hat Enterprise Linux 8 update for kernel
• Anolis OS update for kernel:4.18