CVE-2026-45890 xen-netback: reject zero-queue configuration from guest
A malicious Xen guest can cause a host denial of service by setting zero queues, triggering a kernel warning that panics the system if panic_on_warn is enabled.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-45890?
CVE-2026-45890 is a medium-severity denial of service vulnerability in Linux kernel, published on 27 May 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
xen-netback: reject zero-queue configuration from guest
A malicious or buggy Xen guest can write "0" to the xenbus key "multi-queue-num-queues". The connect() function in the backend only validates the upper bound (requested_num_queues > xenvif_max_queues) but not zero, allowing requested_num_queues=0 to reach vzalloc(array_size(0, sizeof(struct xenvif_queue))), which triggers WARN_ON_ONCE(!size) in __vmalloc_node_range().
On systems with panic_on_warn=1, this allows a guest-to-host denial of service.
The Xen network interface specification requires the queue count to be "greater than zero".
Add a zero check to match the validation already present in xen-blkback, which has included this guard since its multi-queue support was added.
Which versions are affected by CVE-2026-45890?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-45890?
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-2026-45890 being exploited?
There is no known exploitation of CVE-2026-45890 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-45890, DEBIAN-CVE-2026-45890, GHSA-jc43-3m97-6p35, ROOT-OS-DEBIAN-11-CVE-2026-45890, ROOT-OS-UBUNTU-2204-CVE-2026-45890, ROOT-OS-UBUNTU-2404-CVE-2026-45890 and 1 more.