CVE-2026-23557 Xenstored DoS via XS_RESET_WATCHES command

What is CVE-2026-23557?

CVE-2026-23557 is a medium-severity denial of service vulnerability in Xen Xen, published on 19 May 2026. It can only be exploited from the same machine or local network, with no action from the victim.

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.

Weakness: CWE-617

Which versions are affected by CVE-2026-23557?

It affects 1 product.

Products include Xen Xen.

How do I fix CVE-2026-23557?

Apply the vendor's patch.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2026-23557 being exploited?

There is no known exploitation of CVE-2026-23557 in the wild and no public exploit code.

Other vulnerabilities in Xen Xen

• CVE-2017-10912 Privilege escalation in n/a Critical 10.0
• CVE-2017-10918 Memory corruption in n/a Critical 10.0
• CVE-2017-10920 Memory corruption in n/a Critical 10.0
• CVE-2017-10921 Memory corruption in n/a Critical 10.0
• CVE-2025-27466 Mutiple vulnerabilities in the Viridian interface Critical 9.8

All Xen Xen vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as ALPINE-CVE-2026-23557, DEBIAN-CVE-2026-23557, GHSA-9879-vj7m-r497, UBUNTU-CVE-2026-23557.