Vulnerability · Published May 19, 2026 · Assigned by XEN
CVE-2026-23557Xenstored DoS via XS_RESET_WATCHES command
Medium 6.5
In plain English
A medium-severity security flaw in Xen from Xen. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 5% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
Any guest can cause xenstored to crash by issuing a XS_RESET_WATCHES command within a transaction due to an assert() triggering. In case xenstored was built with NDEBUG #defined nothing bad will happen, as assert() is doing nothing in this case. Note that the default is not to define NDEBUG for xenstored builds even in release builds of Xen.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine:v3.20 | xen | 4.18.5-r7 | ALPINE-CVE-2026-23557 |
| Alpine:v3.21 | xen | 4.19.5-r2 | ALPINE-CVE-2026-23557 |
| Alpine:v3.22 | xen | 4.20.3-r2 | ALPINE-CVE-2026-23557 |
| Alpine:v3.23 | xen | 4.20.3-r2 | ALPINE-CVE-2026-23557 |
| Alpine:v3.24 | xen | 4.21.1-r3 | ALPINE-CVE-2026-23557 |
| Debian:12 | xen | 4.17.7-0+deb12u1 | DEBIAN-CVE-2026-23557 |
| Debian:13 | xen | 4.20.3+127-gc42374a105-0+deb13u1 | DEBIAN-CVE-2026-23557 |
| Debian:14 | xen | 4.20.3+127-gc42374a105-1 | DEBIAN-CVE-2026-23557 |
| Ubuntu:22.04:LTS | xen | no fix listed | UBUNTU-CVE-2026-23557 |
| Ubuntu:24.04:LTS | xen | no fix listed | UBUNTU-CVE-2026-23557 |
| Ubuntu:25.10 | xen | no fix listed | UBUNTU-CVE-2026-23557 |
| Ubuntu:26.04:LTS | xen | no fix listed | UBUNTU-CVE-2026-23557 |
| Ubuntu:26.10 | xen | no fix listed | UBUNTU-CVE-2026-23557 |
Affected products (as reported)
Weakness: CWE-617 · Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H