CVE-2026-42490 domctl lock open to abuse
Attackers can cause denial of service in Xen hypervisor by exploiting a lock fairness issue when XSM/Flask is enabled.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-42490?
CVE-2026-42490 is a medium-severity vulnerability in Xen, published on 18 Jun 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
[This CNA information record relates to multiple CVEs; the text explains which aspects/vulnerabilities correspond to which CVE.]
To create and manage guests, domctl operations are used by the control domain, a possible Xenstore domain, or by a domain controlling a particular guest. Some of these operations may not be executed in parallel, so a system-wide lock is used. The way that lock is acquired is, however, not providing any fairness. This is CVE-2026-42489.
Furthermore, with XSM/Flask in use, the lock acquire will, for some operations, occur ahead of any permission checking. This is CVE-2026-42490.
Weakness: CWE-667
Which versions are affected by CVE-2026-42490?
How do I fix CVE-2026-42490?
Apply the vendor's patch.
Is CVE-2026-42490 being exploited?
There is no known exploitation of CVE-2026-42490 in the wild and no public exploit code.
Sources
Also known as ALPINE-CVE-2026-42490, DEBIAN-CVE-2026-42490, GHSA-9xq7-8p44-p7p4, UBUNTU-CVE-2026-42490.