Reachable assertion in Xen - CVE-2026-23557
Published: April 28, 2026
Vulnerability identifier: #VU128378
CSH Severity: Medium
CVSS v4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-23557
CWE-ID: CWE-617
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to an assertion failure in xenstored when processing an XS_RESET_WATCHES command within a transaction. A remote attacker can issue a crafted XS_RESET_WATCHES command within a transaction to cause a denial of service.
Only systems using the C variant of xenstored or xenstore-stubdom built without NDEBUG are vulnerable.
Affected software
Xen
SUSE Linux Enterprise Server 15 SP6
SUSE Linux Enterprise Server 12 SP5 LTSS Extended
SUSE Linux Enterprise Server 15 SP5
SUSE Linux Enterprise Server 12 SP5
SUSE Linux Enterprise High Performance Computing 12
SUSE Linux Enterprise Server 12
SUSE Linux Enterprise Server for SAP Applications 12
SUSE Linux Enterprise High Performance Computing 15
SUSE Linux Enterprise High Performance Computing ESPOS 15
SUSE Linux Enterprise High Performance Computing LTSS 15
SUSE Linux Enterprise Server 15
SUSE Linux Enterprise Server for SAP Applications 15
SUSE Linux Enterprise Real Time 15
SUSE Linux Enterprise Desktop 15
SUSE Linux Enterprise Micro
SUSE Linux Enterprise Micro for Rancher
Basesystem Module
Server Applications Module
openSUSE Leap
Fedora
xen-devel
xen
xen-libs-debuginfo
xen-tools-domU
xen-libs-32bit
xen-debugsource
xen-tools-debuginfo
xen-tools-domU-debuginfo
xen-tools
xen-doc-html
xen-libs-debuginfo-32bit
xen-libs
xen-libs-64bit
xen-libs-32bit-debuginfo
xen-tools-xendomains-wait-disk
xen-libs-64bit-debuginfo
SUSE Linux Enterprise Server 15 SP6
SUSE Linux Enterprise Server 12 SP5 LTSS Extended
SUSE Linux Enterprise Server 15 SP5
SUSE Linux Enterprise Server 12 SP5
SUSE Linux Enterprise High Performance Computing 12
SUSE Linux Enterprise Server 12
SUSE Linux Enterprise Server for SAP Applications 12
SUSE Linux Enterprise High Performance Computing 15
SUSE Linux Enterprise High Performance Computing ESPOS 15
SUSE Linux Enterprise High Performance Computing LTSS 15
SUSE Linux Enterprise Server 15
SUSE Linux Enterprise Server for SAP Applications 15
SUSE Linux Enterprise Real Time 15
SUSE Linux Enterprise Desktop 15
SUSE Linux Enterprise Micro
SUSE Linux Enterprise Micro for Rancher
Basesystem Module
Server Applications Module
openSUSE Leap
Fedora
xen-devel
xen
xen-libs-debuginfo
xen-tools-domU
xen-libs-32bit
xen-debugsource
xen-tools-debuginfo
xen-tools-domU-debuginfo
xen-tools
xen-doc-html
xen-libs-debuginfo-32bit
xen-libs
xen-libs-64bit
xen-libs-32bit-debuginfo
xen-tools-xendomains-wait-disk
xen-libs-64bit-debuginfo
How to mitigate CVE-2026-23557
Install security update from vendor's website.
xen-devel - addressed in versions 4.12.4_68-3.142.1, 4.14.6_30-150300.3.97.1, 4.16.7_08-150400.4.81.2, 4.17.6_08-150500.3.65.1, 4.18.5_16-150600.3.45.1, 4.20.3_02-150700.3.33.1, 4.20.3_04-150700.3.36.1
xen - addressed in versions 4.12.4_68-3.142.1, 4.14.6_30-150300.3.97.1, 4.16.7_08-150400.4.81.2, 4.17.6_08-150500.3.65.1, 4.18.5_16-150600.3.45.1, 4.20.3_02-150700.3.33.1, 4.20.3_04-150700.3.36.1
xen-libs-debuginfo - addressed in versions 4.12.4_68-3.142.1, 4.14.6_30-150300.3.97.1, 4.16.7_08-150400.4.81.2, 4.17.6_08-150500.3.65.1, 4.18.5_16-150600.3.45.1, 4.20.3_02-150700.3.33.1, 4.20.3_04-150700.3.36.1
xen-tools-domU - addressed in versions 4.12.4_68-3.142.1, 4.14.6_30-150300.3.97.1, 4.16.7_08-150400.4.81.2, 4.17.6_08-150500.3.65.1, 4.18.5_16-150600.3.45.1, 4.20.3_02-150700.3.33.1, 4.20.3_04-150700.3.36.1
xen-libs-32bit - addressed in versions 4.12.4_68-3.142.1, 4.14.6_30-150300.3.97.1, 4.16.7_08-150400.4.81.2, 4.17.6_08-150500.3.65.1, 4.18.5_16-150600.3.45.1
xen-debugsource - addressed in versions 4.12.4_68-3.142.1, 4.14.6_30-150300.3.97.1, 4.16.7_08-150400.4.81.2, 4.17.6_08-150500.3.65.1, 4.18.5_16-150600.3.45.1, 4.20.3_02-150700.3.33.1, 4.20.3_04-150700.3.36.1
xen-tools-debuginfo - addressed in versions 4.12.4_68-3.142.1, 4.14.6_30-150300.3.97.1, 4.16.7_08-150400.4.81.2, 4.17.6_08-150500.3.65.1, 4.18.5_16-150600.3.45.1, 4.20.3_02-150700.3.33.1, 4.20.3_04-150700.3.36.1
xen-tools-domU-debuginfo - addressed in versions 4.12.4_68-3.142.1, 4.14.6_30-150300.3.97.1, 4.16.7_08-150400.4.81.2, 4.17.6_08-150500.3.65.1, 4.18.5_16-150600.3.45.1, 4.20.3_02-150700.3.33.1, 4.20.3_04-150700.3.36.1
xen-tools - addressed in versions 4.12.4_68-3.142.1, 4.14.6_30-150300.3.97.1, 4.16.7_08-150400.4.81.2, 4.17.6_08-150500.3.65.1, 4.18.5_16-150600.3.45.1, 4.20.3_02-150700.3.33.1, 4.20.3_04-150700.3.36.1
xen-doc-html - addressed in versions 4.12.4_68-3.142.1, 4.14.6_30-150300.3.97.1, 4.16.7_08-150400.4.81.2, 4.17.6_08-150500.3.65.1, 4.18.5_16-150600.3.45.1
xen-libs-debuginfo-32bit - update to 4.12.4_68-3.142.1
xen-libs - addressed in versions 4.12.4_68-3.142.1, 4.14.6_30-150300.3.97.1, 4.16.7_08-150400.4.81.2, 4.17.6_08-150500.3.65.1, 4.18.5_16-150600.3.45.1, 4.20.3_02-150700.3.33.1, 4.20.3_04-150700.3.36.1
xen-libs-64bit - addressed in versions 4.14.6_30-150300.3.97.1, 4.16.7_08-150400.4.81.2, 4.17.6_08-150500.3.65.1, 4.18.5_16-150600.3.45.1
xen-libs-32bit-debuginfo - addressed in versions 4.14.6_30-150300.3.97.1, 4.16.7_08-150400.4.81.2, 4.17.6_08-150500.3.65.1, 4.18.5_16-150600.3.45.1
xen-tools-xendomains-wait-disk - addressed in versions 4.14.6_30-150300.3.97.1, 4.16.7_08-150400.4.81.2, 4.17.6_08-150500.3.65.1, 4.18.5_16-150600.3.45.1, 4.20.3_02-150700.3.33.1, 4.20.3_04-150700.3.36.1
xen-libs-64bit-debuginfo - addressed in versions 4.14.6_30-150300.3.97.1, 4.16.7_08-150400.4.81.2, 4.17.6_08-150500.3.65.1, 4.18.5_16-150600.3.45.1
xen - addressed in versions 4.19.5-2.fc42, 4.20.3-2.fc43, 4.21.1-2.fc44
xen - addressed in versions 4.12.4_68-3.142.1, 4.14.6_30-150300.3.97.1, 4.16.7_08-150400.4.81.2, 4.17.6_08-150500.3.65.1, 4.18.5_16-150600.3.45.1, 4.20.3_02-150700.3.33.1, 4.20.3_04-150700.3.36.1
xen-libs-debuginfo - addressed in versions 4.12.4_68-3.142.1, 4.14.6_30-150300.3.97.1, 4.16.7_08-150400.4.81.2, 4.17.6_08-150500.3.65.1, 4.18.5_16-150600.3.45.1, 4.20.3_02-150700.3.33.1, 4.20.3_04-150700.3.36.1
xen-tools-domU - addressed in versions 4.12.4_68-3.142.1, 4.14.6_30-150300.3.97.1, 4.16.7_08-150400.4.81.2, 4.17.6_08-150500.3.65.1, 4.18.5_16-150600.3.45.1, 4.20.3_02-150700.3.33.1, 4.20.3_04-150700.3.36.1
xen-libs-32bit - addressed in versions 4.12.4_68-3.142.1, 4.14.6_30-150300.3.97.1, 4.16.7_08-150400.4.81.2, 4.17.6_08-150500.3.65.1, 4.18.5_16-150600.3.45.1
xen-debugsource - addressed in versions 4.12.4_68-3.142.1, 4.14.6_30-150300.3.97.1, 4.16.7_08-150400.4.81.2, 4.17.6_08-150500.3.65.1, 4.18.5_16-150600.3.45.1, 4.20.3_02-150700.3.33.1, 4.20.3_04-150700.3.36.1
xen-tools-debuginfo - addressed in versions 4.12.4_68-3.142.1, 4.14.6_30-150300.3.97.1, 4.16.7_08-150400.4.81.2, 4.17.6_08-150500.3.65.1, 4.18.5_16-150600.3.45.1, 4.20.3_02-150700.3.33.1, 4.20.3_04-150700.3.36.1
xen-tools-domU-debuginfo - addressed in versions 4.12.4_68-3.142.1, 4.14.6_30-150300.3.97.1, 4.16.7_08-150400.4.81.2, 4.17.6_08-150500.3.65.1, 4.18.5_16-150600.3.45.1, 4.20.3_02-150700.3.33.1, 4.20.3_04-150700.3.36.1
xen-tools - addressed in versions 4.12.4_68-3.142.1, 4.14.6_30-150300.3.97.1, 4.16.7_08-150400.4.81.2, 4.17.6_08-150500.3.65.1, 4.18.5_16-150600.3.45.1, 4.20.3_02-150700.3.33.1, 4.20.3_04-150700.3.36.1
xen-doc-html - addressed in versions 4.12.4_68-3.142.1, 4.14.6_30-150300.3.97.1, 4.16.7_08-150400.4.81.2, 4.17.6_08-150500.3.65.1, 4.18.5_16-150600.3.45.1
xen-libs-debuginfo-32bit - update to 4.12.4_68-3.142.1
xen-libs - addressed in versions 4.12.4_68-3.142.1, 4.14.6_30-150300.3.97.1, 4.16.7_08-150400.4.81.2, 4.17.6_08-150500.3.65.1, 4.18.5_16-150600.3.45.1, 4.20.3_02-150700.3.33.1, 4.20.3_04-150700.3.36.1
xen-libs-64bit - addressed in versions 4.14.6_30-150300.3.97.1, 4.16.7_08-150400.4.81.2, 4.17.6_08-150500.3.65.1, 4.18.5_16-150600.3.45.1
xen-libs-32bit-debuginfo - addressed in versions 4.14.6_30-150300.3.97.1, 4.16.7_08-150400.4.81.2, 4.17.6_08-150500.3.65.1, 4.18.5_16-150600.3.45.1
xen-tools-xendomains-wait-disk - addressed in versions 4.14.6_30-150300.3.97.1, 4.16.7_08-150400.4.81.2, 4.17.6_08-150500.3.65.1, 4.18.5_16-150600.3.45.1, 4.20.3_02-150700.3.33.1, 4.20.3_04-150700.3.36.1
xen-libs-64bit-debuginfo - addressed in versions 4.14.6_30-150300.3.97.1, 4.16.7_08-150400.4.81.2, 4.17.6_08-150500.3.65.1, 4.18.5_16-150600.3.45.1
xen - addressed in versions 4.19.5-2.fc42, 4.20.3-2.fc43, 4.21.1-2.fc44